LIBRARY 

OF  THE 

UNIVERSITY  OF  CALIFORNIA. 


Class 


PORTLAND  CEMENT 


Its  Composition,  Raw  Materials,  Manu- 
facture, Testing  and  Analysis 


BY 


RICHARD  K.  MEADE,  B.  S. 
f  • 

CHEMIST  TO  THE  DEXTER  PORTLAND  CEMENT  COMPANY,  EDITOR 

OF  "THE  CHEMICAL  ENGINEER,"  AUTHOR  OF  THE 
•  CHEMISTS'  POCKET  MANUAL,  ETC. 


EASTON.  PA. 

THE  CHEMICAL  PUBLISHING  COMPANY 
1906 


COPYRIGHT,  1906,  BY  THE  CHEMICAL  PUBLISHING  Co. 


PREFACE. 


The  present  treatise  upon  Portland  cement  is  really  the  second 
edition  of  a  small  manual  by  the  writer,  published  some  four  years 
ago,  called  "The  Chemical  and  Physical  Examination  of  Portland 
Cement."  In  preparing  this  new  edition,  it  seemed  wise  to  add  a 
section  on  the  manufacture  of  Portland  cement,  for  the  reason 
that  the  chemist  who  is  to  intelligently  supervise  the  process  of 
manufacture,  as  well  as  the  chemist  who  is  to  report  upon  the 
raw  materials  and  the  engineer  who  is  to  inspect  the  product, 
should  have  a  good,  general  knowledge  of  the  technology  of 
Portland  cement. 

It  was  also  found  necessary  to  rewrite  almost  the  entire  section 
upon  the  physical  testing  of  cement  in  order  to  give  special  promi- 
nence to  the  uniform  methods  of  testing  adopted  by  the  American 
Society  of  Civil  Engineers,  and  to  the  standard  specifications  of 
the  American  Society  for  Testing  Materials.  Much  new  matter 
has  also  been  added  to  the  section  on  the  analysis  of  cement  and 
its  raw  materials,  and  sections  on  the  experimental  manufacture 
of  small  lots  of  cement  and  on  the  history  of  the  industry  have 
been  included. 

The  analytical  methods  have  all  been  used  to  some  extent  in 
the  writer's  laboratory  and  have  been  found  satisfactory.  Com- 
ments as  to  their  accuracy  and  advice  as  to  the  best  methods  of 


IV 

manipulation  will  usually  be  found  with  each  method  under  the 
heading,  "notes." 

The  author  again  wishes  to  thank  the  many  friends  who  have 
aided  him  in  the  preparation  of  both  this  and  the  former  edition. 

NAZARETH,  PA.,  July,  1906. 


CONTENTS. 


INTRODUCTION. 

Chapter  I — History  of  the  Development  of  the  American 

Portland  Cement  Industry   1-14 

The  Beginning  of  the  Industry  in  England,  I ;  Inven- 
tion of  Portland  Cement,  2;  Discovery  of  Cement 
Rock  in  the  United  States,  4;  Production  of  Natural 
Cement  in  the  United  States,  6;  Beginning  of  the 
Portland  Cement  Industry  in  the  United  States,  8; 
Development  in  Other  States,  9;  Production  of  Port- 
land Cement  in  the  United  States,  n. 

Chapter  II — Chemical  Composition  of  Portland  Cement.  15-32 
Composition  of  Cement,  15;  Analysis  of  Various 
American  Portland  Cements,  16;  Analysis  of  Foreign 
Portland  Cements,  17;  Theory  of  the  Hardening  of 
Cement,  18;  Hydraulic  Index,  19;  Messrs.  Newberrys' 
Theory,  19;  Newberry's  Formula,  20;  Tornebohm's 
Investigations,  20 ;  Richardson's  Work,  21 ;  Solid  Solu- 
tion Theory,  23;  Substances  Found  in  Cement,  24; 
Lime,  25;  Silica,  27;  Alumina,  27;  Ferric  Oxide,  28; 
Magnesia,  29;  Alkalies,  30;  Sulphur,  30;  Carbon  Diox- 
ide and  Water,  31 ;  Other  Compounds  in  Portland 
Cement,  32. 

MANUFACTURE. 

Chapter  III — Raw  Materials   33-51 

Essential  Elements,  33 ;  Classification  of  Materials,  33 ; 
Limestone,  34;  Cement  Rock,  35;  Marl,  40;  Clay,  44; 
Shale,  45;  Blast  Furnace  Slag,  46;  Alkali  Waste,  47; 
Gypsum,  48;  The  Valuation  of  Raw  Materials,  49. 

Chapter  IV — Proportioning  the  Raw  Materials S2~7° 

Introduction,  52;  Fixed  Lime  Standard,  60;  Formulas 
for  a  Fixed  Lime  Standard,  61 ;  Controlling  the  Mix- 
ture in  the  Wet  Process,  67. 

Chapter  V — Quarrying,  Excavating,  Drying  and  Mixing 

the  Raw  Materials   7J-83 

8 uarrying  the  Stone,  71 ;  Excavating  Marl,  73 ;  Stone 
ouses,    75 ;    Wet    Process,    78 ;    Examples    of    Treat- 
ment  of   Raw    Material    Preparatory   to    Fine    Grind-  ' 
ing,  79- 
Chapter  VI — Grinding  the  Raw  Material  and  Grinding 

Machinery    84-99 

Crushers,  84;  Gates  Crusher,  85;  Blake  Crusher,  86* 
Griffin  Mill,  87;  Three  Roll  Griffin  Mill,  89;  Hunting- 


VI  CONTENTS 

ton  Mill,  91;  Ball  Mill,  92;  Kominuter,  95;  Tube  Mill, 
95 ;  Capacity  of  Various  Grinders,  97 ;  Degree  of  Fine- 
ness, 98 ;  Conveyors,  99. 
Chapter  VII — Kilns  and  Burning 100-145 

Shaft  Kilns,  100;  The  Rotary  Kiln,  106;  Fuel,  112; 
Grinding  the  Coal,  114;  Burning  with  Natural  and 
Producer  Gas,  118;  Kiln  Lining,  121;  Chemical 
Changes  Undergone  in  Burning,  123;  Degree  of  Burn- 
ing, 132;  Thermo-Chemistry  of  Burning,  133;  Excess 
of  Air  Used  in  Burning,  139;  Utilization  of  Waste 
Heat,  141. 

Chapter  VIII — Cooling  and  Grinding  the  Clinker,  Stor- 
ing and  Packing  the  Cement,  Etc 146-165 

Cooling  the  Clinker,  146;  Grinding  the  Clinker,  148; 
Kent  Mill,  149;  Air  Separators,  150;  Stock  Houses, 
153;  Packing,  154;  Power  Plant,  155;  Complete  Equip- 
ment of  Plants,  157;  References  to  Descriptions  of. 
Plants,  157;  Cost  of  Plant  and  Manufacture,  161. 

ANALYTICAL  METHODS. 

Chapter  IX — The  Analysis  of  Cement - .  . .  .    166-224 

Sampling,  166;  Samplers,  167;  Determination  of 
Silica,  Ferric  Oxide  and  Alumina,  Lime  and  Mag- 
nesia, i/o;  Volumetric  Determination  of  Lime,  185; 
Rapid  Determination  of  Lime  Without  Separation  of 
Silica,  Etc.,  189;  Determination  of  Ferric  Oxide,  190; 
Determination  of  Sulphuric  Acid,  200;  Determination 
of  Total  Sulphur,  203;  Determination  of  Sulphur 
Present  as  Calcium  Sulphide,  204;  Loss  on  Ignition, 
208;  Determination  of  Carbon  Dioxide  and  Water, 
209;  Determination  of  Carbon  Dioxide  Alone,  215; 
Rapid  Determination  of  Carbon  Dioxide,  216;  Deter- 
mination of  Hygroscopic  Water,  218 ;  Determination 
of  Alkalies,  220;  Determination  of  Phosphoric  Acid, 
222;  Determination  of  Manganese,  223;  Determina- 
tion of  Titanium,  224. 
Chapter  X — The  Analysis  of  Cement  Mixtures,  Slurry, 

Etc    225-251 

Sampling,  225;  Rapid  Methods  for  Checking  the  Per- 
centage  of    Calcium    Carbonate    in    Cement    Mixtures, 
231;  Determination  of  Silicates,  247;  Complete  Analy- 
sis of  Cement  Mixtures  or  Slurry,  248. 
Chapter  XI — The  Analysis  of  the  Raw  Materials 252-271 

Sampling,  252;  Methods  for  Limestone,  Cement  Rock 
and  Marl,  254 ;  Methods  for  Clay  and  Shale,  261 ; 
Methods  for  Gypsum  or  Plaster  of  Paris,  269. 

PHYSICAL  TESTING, 

Chapter  XII — The  Inspection  of  Cement 272-277 

Tests  to  be   Made,   272;    Method   of   Inspection,   273; 


CONTENTS  VJ1 

Inspection  at  Mill,  273;  Inspection  on  the  Work,  276; 
Uniform  Specifications  and  Methods  of  Testing,  277. 

Chapter  XIII — Specific  Gravity   278-290 

Standard  Specifications  and  Method  of  Test,  278 ; 
Other  Methods,  280;  With  Schumann-Candlot  Ap- 
paratus, 280 ;  Jackson's  Apparatus,  281 ;  Simple  Ap- 
paratus for  Specific  Gravity,  286;  WTith  Specific  Grav- 
ity Bottle,  288 ;  Observations  on  Specific  Gravity,  289 ; 
Test  of  Little  Value  Alone,  289. 

Chapter  XIV — Fineness    291-298 

Standard  Specifications  and  Method  of  Test,  291 ; 
Other  Methods,  292 ;  Method  of  Sieving,  Sieves,  Etc., 
292 ;  Errors  in  Sieves,  293 ;  Observations  on  Fineness, 
294;  Limitations  of  Sieve  Test,  294;  Determining  the 
Flour  in  Cement,  296. 

Chapter  XV — Time  of  Setting   299-315 

Standard  Specification  and  Method  of  Test,  299; 
Normal  Consistency,  299;  Time  of  Setting,  300; 
Other  Methods,  301 ;  Observations  on  Setting  Time, 
303 ;  Factors  Influencing  the  Rate  of  Setting,  303 ;  Rise 
in  Temperature  During  Setting,  305 ;  Influence  of  Sul- 
phates on  Setting  Properties,  306;  Influence  of  Cal- 
cium Chloride  on  Setting  Time,  310;  Effect  of  Stor- 
age of  Portland  Cement  on  Its  Setting  Properties, 
311  ;  Influence  of  Slaked  Lime  on  Setting  Time,  314. 

Chapter  XVI — Tensile  Strength   316-350 

Standard  Specification  and  Method  of  Test,  316; 
Standard  Sand,  316;  Form  of  Briquette,  317;  Molds, 
317;  Mixing,  318;  Moulding,  319;  Storage  of  Test 
Pieces,  319;  Tensile  Strength,  320;  Other  Methods, 
321  ;  Standard  Sand,  321 ;  Forms  of  Briquettes,  322 ; 
Molds,  323 ;  Mixing,  325 ;  Percentage  of  Water,  326 ; 
Storage  of  Briquettes,  327;  Testing  Machines,  329; 
Clips,  338;  Lack  of  Uniformity  in  Tensile  Tests,  339; 
Machines  for  Mixing  the  Mortar,  340;  Machines  for 
Molding  the  Briquettes,  342;  Aiken's  Method  of  Mak- 
ing Briquettes,  345 ;  Observations,  346 ;  High  Tensile 
Strength  of  Unsound  Cements,  346;  Effect  of  Grind- 
ing on  Neat  and  Sand  Strength,  347;  Drop  in  Ten- 
sile Strength,  347. 

Chapter   XVII — Soundness    35 1 -365 

Standard  Specification  and  Method  of  Test,  351 ; 
Other  Methods,  351 ;  Faija's  Test,  351 ;  Maclay's  Test, 
352;  Kiln  Test,  354;  Boiling  Test,  355;  Calcium  Chlor- 
ide Test,  355;  Bauschinger's  Calipers,  356;  LeChate- 
lier's  Calipers,  357;  Observations,  358;  Importance  of 
Test,  358;  Causes  of  Unsoundness,  358;  Effect  of 
Seasoning  on  Soundness,  359;  Effect  of  Fine  Grind- 
ing of  the  Raw  Materials  on  Soundness,  360 ;  Effect  of 
Fine  Grinding  of  Cement  Itself  on  Soundness,  361 ; 
Effect  of  Sulphates  on  Soundness,  361 ;  Value  of 
Accelerated  Tests,  362. 


Vlll  CONTENTS 

MISCELLANEOUS 

Chapter  XVIII — The  Detection  of  Adulteration  in  Port- 
land  Cement    366-3/1 

Tests   of   Drs.   R.   and    W.    Fresenius,   366;    Proposed 

Tests,  366;  Carrying  Out  the  Tests,  368;  LeChatelier's 

Test,  369;  Microscopic  Test,  371. 
Chapter  XIX — Trial  Burnings   372~3?6 

Crushing  the  Samples,  372 ;  Jar  Mill,  373 ;  Kilns,  374. 
Appendix-Tables   377-3^0 

Table  of  Atomic  Weights,  377 ;  Table  of  Factors,  377 ; 

Table   for   Converting   Mg2P2O7  to   MgO,   378;   Table 

for  Use  with  Permanganate  in  Lime  Determinations, 

378. 


INTRODUCTION. 


CHAPTER  L 


HISTORY  OF  THE  DEVELOPMENT  OF  THE    AMER- 
ICAN PORTLAND  CEMENT  INDUSTRY. 


The  Beginning  of  the  Industry  in  England. 

The  cement  industry  proper  dates  from  the  researches  of  an 
English  engineer,  John  Smeaton,  who  had  been  employed  by  par- 
liament to  build  a  lighthouse  upon  a  group  of  gneiss  rocks,  in  the 
English  Channel,  just  off  the  coast  of  Cornwall.  These  crags, 
known  as  Eddystone,  were  at  high  tide  under  water  for  some 
hours  and  many  shipwrecks  had  occurred  upon  them.  They  were 
a  menace  to  the  navigation  of  this  part  of  the  channel  and  it  was 
necessary  to  warn  sailors  of  their  whereabouts.  Two  wooden 
structures  built  upon  them  had  been  subjected  to  the  fury  of  the 
elements  and  had  each  experienced  but  a  short  life. 

When  Smeaton  attacked  the  problem,  he  determined  to  build 
a  structure  which  would  weather  the  fiercest  storms  of  the  chan- 
nel and  would  come  out  of  these  an  enduring  monument  to  his 
engineering  skill.  One  of  the  greatest  difficulties  he  had  to  over- 
come was  the  failure  of  ordinary  lime  mortar  (the  discovery  of 
which  dates  back  to  antiquity)  to  harden  under  water.  In  order 
that  his  foundations  should  be  firm,  it  was  necessary  that  some 
mortar  be  found  which  would  meet  this  difficutly.  To  this  end  he 
undertook  a  series  of  investigations  in  1756,  the  result  of  which 
was  the  discovery  that  the  hard,  white,  pure  limestones,  hitherto 
considered  best  for  lime  making,  were  in  reality  inferior  to  the 
soft  clayey  ones1 ;  for  from  these  latter  he  succeeded  in  obtain- 
ing a  lime  far  superior  to  any  then  in  use  because  it  not  only 
hardened  better  in  air,  but  would  also  harden  under  water.  Such 
a  limestone  Smeaton  found  near  at  hand,  at  Aberthaw,  in  Corn- 

1  Smeaton— Narrative  of  the  building,  etc.,  of  the  Eddystone  lighthouse,  Book  IV. 

I 


2  PORTLAND  CEMENT 

• 

wall,  and  the  hydraulic  lime  formed  by  burning  this  stone  was  the 
basis  of  the  mortar  used  in  the  construction  of  the  Eddystone 
lighthouse. 

Smeaton  in  making  his  hydraulic  lime,  however,  used  only 
those  layers  of  his  quarry  which  after  burning  gave  a  product 
that  would  slake  with  water.  The  idea  of  burning  the  layers 
which  would  not  slake  readily  and  then  by  grinding,  convert  them 
into  a  very  energetic  hydraulic  lime  did  not  suggest  itself  to  him 
and  it  was  not  until  forty  years  later  that  this  first  improvement 
was  made  in  the  manufacture  of  hydraulic  lime.  In  1/96,  one 
Joseph  Parker,  of  Northfleet,  in  Kent  Co.,  Eng.,  took  out  a  patent 
for  the  manufacture  of  a  hydraulic  lime  which  he  called  "Roman 
Cement"  and  which  he  made  by  calcining  or  burning  the  argillo- 
calcarious,  kidney-shaped  nodules  called  "septaria"  and  then 
grinding  the  resulting  product  to  a  powder.1  In  composition 
these  nodules  were  very  similar  to  what  we  now  call  Rosendale 
cement  rock.  They  occurred  geologically  in  the  London  clay 
formation  and  were  usually  obtained  from  the  shores  of  the  Isle 
of  Sheppy  where  they  were  washed  up  after  a  storm.  This 
cement  came  rapidly  into  favor  with  the  English  engineers  be- 
cause much  work  could  be  done  with  it  that  was  impossible  with 
quick  lime.  In  1802  cement  was  produced  from  the  same  "sep- 
taria" at  Boulogne,  France,  and  this  was  the  beginning  of  the 
cement  industry  in  that  country. 

In  1810,  Edgar  Dobbs,  of  Southwick,  England,  obtained  a 
patent  for  the  manufacture  of  an  artificial  Roman  cement  by  mix- 
ing carbonate  of  lime  and  clay,  in  suitable  proportions,  moisten- 
ing, molding  into  bricks,  and  burning  sufficiently  to  expel  the 
carbonic  acid,  without  vitrifying  the  mixture.  Soon  after  this, 
General  Sir  Wm.  Paisley,  in  England,  and  L.  J.  Vicat,  a  French 
engineer,  both  independently  of  each  other,  made  exhaustive  ex- 
periments looking  to  the  manufacture  of  an  artificial  Roman  ce- 
ment by  mixing  clay  with  chalk,  etc.  In  1813  Vicat  began  the 
manufacture  of  artificial  hydraulic  cement  in  France,  as  did  also 
James  Frost  in  England,  in  1822. 

Invention  of  Portland  Cement. 
In  1824,  Joseph  Aspdin,  a  bricklayer  of  Leeds,  England,  took 

l  Redgrave— Calcareous  Cements. 


DEVELOPMENT  OF  THE  INDUSTRY  3 

out  a  patent  on  an  improved  cement  which  he  proposed  to  make 
from  the  dust  of  roads  repaired  with  limestone,  or  else  from  lime- 
stone itself  combined  with  clay,  by  burning  and  grinding.  This 
cement  he  called  "Portland  Cement,"  because  when  hardened  it 
produced  a  yellowish  gray  mass  resembling  in  appearance  the 
stone  from  the  famous  quarries  of  Portland,  England. 

At  this  point,  it  seems  proper  to  state  that  there  are  now  manu- 
factured and  sold  in  this  country  three  kinds  of  hydraulic  cement : 

First — Natural,  Natural  Rock,  Rosendale,  or  Roman  cement, 
which  is  made  by  burning  suitable  clayey  limestones  to  the  point 
when  most  of  the  carbonic  acid  is  expelled  and  then  grinding  to  a 
powder  the  resulting  soft  brownish  yellow  clinker. 

Second — Portland  cement  which  is  made  by  grinding  to  an  im- 
palpable powder  a  mixture  of  argillaceous  and  calcareous  sub- 
stances in  proper  proportions,  burning  the  mixture  to  the  point  of 
incipient  vitrifaction  and  then  regrinding  the  resulting  greenish 
black  clinker. 

Finally — Slag  or  Puzzolan  cement  which  is  made  by  grinding 
together  without  subsequent  calcination  a  mixture  of  blast  fur- 
nace slag  and  slaked  lime.  It  is  now  generally  accepted  that  the 
cements  used  by  the  Romans  were  of  this  character  and  were 
made  from  volcanic  slag  called  "Puzzolana"  (from  the  town  Puz- 
zuoli,  at  the  foot  of  Mt.  Vesuvius,  where  its  properties  were  first 
discovered).  It  is  supposed  that  the  Romans  mixed  this  slag  with 
slaked-lime  and  a  small  amount  of  sand  for  their  hydraulic  mor- 
tar. There  are  authorities,  Cummings  among  them,  who  con- 
tend that  the  Romans  knew  how  to  make  Rosendale  or  Natural 
cement  and  that  their  concrete  work  was  done  with  this.1 

Aspdin  is  usually  credited  with  the  invention  of  Portland  ce- 
ment and  while  he  certainly  did  originate  the  name  "Portland 
Cement"  he  probably  did  nothing  more  than  make  an  artificial 
Roman  cement,  which  had  been  done  before,  since  he  apparently 
did  not  carry  his  burning  to  the  point  of  incipient  vitrifaction, 
which  we  now  recognize  as  being  an  essential  point  in  the  manu- 
facture of  Portland  cement.2  Aspdin  erected  a  factory  at 
Waken" eld,  England,  for  the  manufacture  of  his  cement,  which 

1  Cummings — American  Cements. 

J  Michaelis — Thonindustrie  Zeitung,  Jan.  16,  1904. 


4  PORTLAND  CEMENT    - 

was  used  upon  the  Thames  Tunnel  in  1828.  At  first  Portland 
cement  was  sold  at  prices  considerably  lower  than  the  Natural 
or  Roman  cement  of  Parker  and  his  successors,  and  it  was  not 
until  John  Grant,  in  1859,  decided  to  use  Portland  cement  in  the 
construction  of  the  London  drainage  canal,  of  which  he  was  chief 
engineer,  and  published  his  reasons  for  doing  so  in  the  transac- 
tions of  the  Institution  of  Civil  Engineers,  that  the  new  cement 
began  to  come  to  the  front. 

It  is  evident  that  by  this  time  the  value  of  burning  the  clinker 
to  the  point  of  incipient  vitrifaction  had  been  discovered  and 
made  use  of — probably  first  in  the  famous  old  works  of  White  & 
Bros.,  established  by  James  Frost  at  Swanscombe,  in  1825,  and 
still  existent.  In  1852  the  first  German  Portland  cement  works 
were  established  near  Stettin.  The  Germans  were  quick  to  see 
the  value  of  the  new  building  material,  and  with  their  fine  tech- 
nologists soon  turned  out  a  better  product,  by  the  substitution  of 
scientific  methods  in  place  of  rules  of  thumb.  They  were  the  first 
to  appreciate  the  value  of  fine  grinding  of  the  cement,  and  until 
recently  the  German  Portlands  were  the  standard.  Today  prob- 
ably the  best  Portland  cement  made  in  the  world  is  turned  out  in 
America. 

Discovery  of  Cement  Rock  in  the  United  States. 

In  this  country  the  cement  industry  began  with  the  discovery 
in  1818,  of  a  natural  cement  rock  near  Chittenango,  Madison  Co., 
N.  Y.,  by  Mr.  Canvass  White,  an  engineer  engaged  in  the  con- 
struction of  the  Erie  canal,  who  after  some  experimenting  ap- 
plied to  the  State  of  New  York  for  the  exclusive  right  to  manu- 
facture this  cement  for  twenty  years.  The  state  denied  his  re- 
quest but  gave  him  $20,000  in  recognition  of  his  valuable  discov- 
ery.1 His  cement  was  used  in  large  quantities  in  the  construc- 
•  tion  of  the  Erie  canal  and  brought  a  price  of  about  twenty  cents 
a  bushel. 

As  the  greatest  users  of  cement  in  this  country  were  the  canals, 
and  as  they  at  that  time  furnished  the  only  means  for  the  trans- 
portation of  bulky  materials,  there  was  naturally  the  sharpest 
lookout  kept  along  their  line  of  construction  for  limestone  suit- 

1  Sylvester— History  of  Ulster  County,  N.  Y. 


DEVELOPMENT  OF  THE  INDUSTRY  5 

able  for  the  making  of  hydraulic  cement.  In  consequence  of  this, 
nearly  all  the  early  cement  mills  were  started  along  the  line  of, 
and  to  furnish  cement  for,  the  construction  of  some  canal.  In 
1825,  cement  rock  was  discovered  in  Ulster  County,  New  York, 
along  the  line  of  the  Delaware  and  Hudson  canal  and  in  the  fol- 
lowing year  a  mill  was  started  at  High  Falls  in  that  county.  In 
1828,  a  mill  was  built  at  Rosendale,  also  in  Ulster  County.  This 
soon  became  the  center  of  the  industry  and  the  cement  made  here 
was  called  Rosendale.  This  name  is  still  largely  applied  to  Ameri- 
can natural  cements.  The  first  cement  was  made  in  small  upright 
kilns.  Wood  was  used  as  fuel  and  the  burning  continued  for 
about  a  week.  The  clinker  was  then  ground  between  mill  stones 
by  water  power.  After  these  mills  had  been  in  operation  several 
years  continuous  kilns  were  introduced  which  permitted  the  clink- 
er to  be  drawn  daily,  coal  being  used  as  fuel. 

In  1829  cement  rock  was  discovered  near  Louisville,  Ky.,  while 
constructing  the  Louisville  &  Portland  Canal,  and  John  Hulme  & 
Co.  almost  immediately  began  the  manufacture  of  Louisville  ce- 
ment at  Shippingport,  a  suburb  of  Louisville.1 

During  the  construction  of  the  Chesapeake  and  Ohio  Canal, 
cement  rock  was  discovered,  in  1836,  in  Maryland,  at  Round  Top, 
near  Hancock,  and  it  has  been  manufactured  there  ever  since. 
Other  canals  along  whose  lines  cement  rock  was  discovered  with 
the  location  and  date,  are  the  Illinois  and  Michigan  Canal,  at 
Utica,  in  1838;  James  River  Canal,  at  Balcony  Falls,  Va.,  in 
1848;  and  Lehigh  Coal  and  Navigation  Co.  Canal,  at  Siegfried, 
Pa.,  in  1850.  At  all  of  these  points  the  manufacture  of  cement 
has  been  continuous.  Other  well  known  brands  of  cement  began 
to  be  manufactured  as  follows:  Akron,  N.  Y.,  1840;  Ft.  Scott, 
Kan.,  1868;  Buffalo,  N.  Y.,  1874;  and  Milwaukee,  Wis.,  in  1875. 

The  process  for  making  natural  cement  is  in  general  as  follows : 
The  rock  is  blasted  down  from  the  face  of  the  quarry,  broken  by 
hand  with  sledges  into  sizes  suitable  for  the  kiln,  loaded  on  dump 
cars  and  elevated  to  the  mouth  of  the  kilns.  Here  the  rock  is 
dumped  into  the  kiln  alternately  with  coal,  a  layer  of  rock  and 
then  a  layer  of  coal.  The  charging  is  kept  up  continuously  dur- 
ing the  daytime  but  hardly  ever  at  night.  As  the  charge  works 

1  I^esley— Jour.  Assoc.  Eng.  Socs.,  Vol.  XV.,  p.  198. 


PORTLAND  CEMENT 


its  way  down  through  the  kiln  it  becomes  calcined  and  the  larger 
portion  of  its  carbonic  acid  driven  off.  When  it  reaches  the  base 
of  the  kiln  it  is  drawn  out  and  conveyed  to  the  grinding  machin- 
ery. The  kilns  used  for  the  manufacture  of  natural  cement  are 
usually  made  of  iron  plates  riveted  together  and  lined  with  fire 
brick.  They  are  circular  in  shape,  upright,  and  their  average 
dimensions  are  about  16  feet  in  diameter  by  45  feet  in  height. 

The  clinker  is  usually  ground  by  buhr-stones,  the  fine  material 
in  many  mills  being  separated  from  the  coarse  by  passing  over 
screens,  so  placed  as  to  allow  the  fine  particles  to  go  to  the  store- 
house and  to  return  the  coarse  ones  to  the  grinders.  The  buhr- 
stones  are  preceeded  by  crushers  or  crackers  to  reduce  the  clinker 
to  a  suitable  size  for  them  to  handle.  In  some  instances  ball  and 
tube  mills  and  Griffin  mills  have  been  installed  in  natural  cement 
plants,  particularly  where  these  plants  also  make  Portland,  but 
the  clinker  from  these  kilns  is  usually  so  soft  as  to  be  easily 
ground  by  buhr-stones. 

There  are  now  in  this  country  between  60  and  70  mills  manu- 
facturing natural  cement.  Below  are  some  figures  on  the  pro- 
duction of  natural  cement  in  this  country. 

TABLE  I.— PRODUCTION  OF  NATURAL  CEMENT  IN  UNITED 

STATES,  1818-1904. 
(Mineral  Resources  of  the  United  States,  1904.) 


Year. 

Barrels. 

Year. 

Barrels. 

Year. 

Barrels. 

1818  to  1830 

300,000 

1885 

4,100,000 

1896 

7.970,450 

1830  to  1840 

/1,  000,000 

1886 

4,186,152 

1897 

8,311,688 

1840  to  1850 

4,250,000 

1887 

6,692,744 

1898 

8,418,924 

1850  to  1860 

ill,  OOO,OOO 

1888 

6,253,295 

I899 

9,868,179 

1860  to  1870 

^  16,420,000 

1889 

6,531,876 

1900 

8,383,519 

1870  to  1880 

22,000,000 

1890 

7,082,204 

1901 

7,084,823 

1880 

2,030,000 

I89I 

7,451,535 

1902 

8,044,305 

1881 

2,440,000 

I892 

8,211,181 

1903 

7,030,271 

1882 

3,165,000 

1893 

7.4n,8i5 

1904 

4,866,331 

1883 

4,190,000 

1894 

1  7,563,488 

• 

1884 

J  4,000,000 

1895 

7.741,077 

DEVELOPMENT  OF  THE  INDUSTRY 


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8  PORTLAND  CEMENT 

It  will  be  noticed  that  there  is  little  increase  in  the  production 
of  natural  cement  since  1890.  This  is  due  to  the  fact  that  since 
that  time  Portland  cement  has  been  fast  displacing  natural  ce- 
ment. The  increase  in  production  in  1900  was  due  to  the  strong 
demand  for  building  materials  that  year;  a  demand  that  could 
not  be  supplied  by  the  Portland  cement  manufacturers.  Our  im- 
ports in  1900  were  over  3,000,000  barrels  of  Portland,  in  spite  of 
the  fact  that  the  home  mills  produced  over  3,000,000  barrels  more 
than  in  1899. 
Beginning  of  the  Portland  Cement  Industry  in  the  United  States. 

As  we  have  stated  cement  rock  was  discovered  in  1850  at  Sieg- 
fried, in  Northampton  Co.,  Pa.,  on  the  line  of  the  Lehigh  Coal 
and  Navigation  Co.'s  canal  leading  from  Easton  to  Mauch  Chunk. 
As  the  cement  for  the  canal  had  to  be  brought  from  New  York, 
the  discovery  was  a  valuable  one  and  was  put  to  immediate  use 
by  the  erection  of  a  mill  at  Siegfried. 

In  the  spring  of  1866,  Messrs.  David  O.  Saylor,  Esaias  Rehrig 
and  Adam  Woolever,  three  gentlemen,  of  Allentown,  Pa.,  formed 
the  Coplay  Cement  Co.,  and  located  a  mill  at  Coplay,  near  Allen- 
town,  and  not  far  from  Siegfried.  Mr.  Saylor  was  president 
and  superintendent  of  the  company.  The  plant  made  excellent 
cement  though  its  methods  for  doing  so  were  crude.  Early  in  the 
seventies  Mr.  Saylor  began  to  experiment  upon  the  manufacture 
of  Portland  cement  from  the  rocks  of  his  quarry.  No  Portland 
cement  was  made  in  this  country  then,  and  most  of  it  in  use  here 
came  from  England  and  Germany.  Its  reputation  was  established 
and  it  was  looked  upon  as  superior  to  Rosendale  cement. 

Mr.  Saylor  was  led  to  make  his  experiments  by  the  fact  that  he 
noticed  the  harder  burned  portions  of  his  Rosendale  clinker  gave 
a  cement  which  for  a  short  period  would  show  a  tensile  strength 
equal  to  that  of  the  best  imported  Portland;  but  he  found  this 
cement  would  crumble  away  with  time.  This  was  due  to  the  raw 
materials  not  being  properly  proportioned.  The  result  of  these 
experiments  taught  him  that  if  he  mixed  a  certain  amount  of 
cement  rock  high  in  lime  with  his  ordinary  cement  rock  he  could 
make  Portland  cement,  and  after  many  trial  lots  were  burned  the 
company  turned  out  its  first  Portland  in  1875.  This  was  the  first 


DEVELOPMENT  OF  THE  INDUSTRY  9 

Portland  cement  made  in  the  Lehigh  District,  and  it  was  made 
from  a  material  totally  different  from  that  used  in  any  of  the 
European  mills. 

The  drawings  for  the  first  kilns  were  made  by  James  Cabott 
Arch,  an  English  engineer,  and  were  bottle-shaped. 

Having  solved  the  problem  of  how  to  make  Portland  cement, 
Say  lor  found  another  and  equally  difficult  one  awaiting  him  of 
how  to  sell  it,  after  it  was  made.  The  labor  cost  of  manufactur- 
ing his  cement  was  great  and  he  could  not  afford  to  offer  it  at 
prices  much  below  the  imported  article.  As  the  foreign  cements 
had  an  established  record,  they  fought  the  new  cement  with  the 
argument  that  any  brand  of  Portland  cement  required  time  to 
prove  itself,  and  it  was  only  by  liberal  advertising  and  an  iron- 
clad guarantee  of  his  product  that  Saylor  secured  a  market. 

Among  the  first  great  engineering  works  upon  whose  construc- 
tion Say  lor 's  Portland  cement  was  used  were  the  Eads  jetties 
along  the  Mississippi  River,  and  the  first  great  sky-scraper  in 
which  American  Portland  cement  was  used  was  the  Drexel  Build- 
ing in  Philadelphia.  Slowly  American  Portland  cement  overcame 
the  prejudice  against  it  and  it  is  now  recognized  as  superior  to 
that  manufactured  in  any  part  of  the  world.  Savior's  original 
plant  turned  out  only  1,700  barrels  of  Portland  cement  a  year. 
Since  its  inception,  however,  it  has  grown  steadily  and  now  has  a 
capacity  of  considerably  over  this  amount  a  day. 
Development  in  Other  States. 

While  Saylor  was  conducting  his  experiments  in  the  Lehigh 
Valley,  a  Chicago  concern,  known  as  the  Eagle  Portland  Cement 
Co.,  built  a  plant  near  Kalamazoo,  Mich.,  about  1872,  to  manu- 
facture Portland  cement  from  marl  and  clay.  This  plant  at  first 
consisted  of  two  bottle-shaped  kilns,  which  number  was  after- 
wards increased  to  four.  The  product  was  known  as  "Eagle 
Portland  Cement,"  and  its  quality  must  have  been  excellent  as 
some  three  of  four  miles  of  sidewalk  put  down  in  Kalamazoo  are 
still  in  good  condition.  This  mill,  however,  was  forced  to  shut 
down  in  1882,  for  although  its  product  sold  at  from  $4  to  $4.25 
per  barrel,  it  could  not  manufacture  cement  at  a  figure  below  this. 
Today  no  traces  of  even  the  kilns  remain.1 

1  Russell— Twenty-second  Annual  Report,  U.  S.  Geological  Survey,  Part  III. 


IO  PORTLAND  CEMENT 

At  Wampum,  Pa.,  a  small  plant  was  started  to  make  cement 
from  limestone  and  clay,  in  1875.  Thomas  Millen  found,  at  South 
Bend,  Ind.,  a  white  marl  and  clay  which  resembled  in  composi- 
tion, the  material  used  for  cement  making  in  England,  and  started 
a  small  plant  there  in  i877.2  Both  the  plants  at  Wampum  and 
South  Bend,  Ind.,  are  now  producers,  though  in  a  modest  way.  In 
Maine  also  a  small  plant  was  started  by  the  Cobb  Lime  Co.,  at 
Rockport,  in  1879,  ^ut  tms  to°  failed  to  make  cement  at  a  figure 
below  its  selling  price  and  closed  down  permanently  as  did  also  a 
small  plant  in  the  Rosendale  district  started  about  the  same  time. 

Of  the  six  works  started  prior  to  1881  half  that  number  were 
failures  and  represented  a  complete  loss  to  their  promoters.  The 
cement  made  at  Coplay  and  Wampum,  however,  was  on  exhibi- 
tion at  the  Philadelphia  Centennial  in  1876,  and  held  its  own  with 
the  imported  article. 

About  1883,  a  small  plant  for  the  manufacture  of  Port- 
land cement  was  inaugurated  at  Egypt,  Pa.,  near  Coplay,  by 
Robt.  W.  Lesley,  the  first  president  of  the  recently  formed 
American  Association  of  Portland  Cement  Manufacturers,  John 
W.  Eckert,  Savior's  first  chemist,  and  others.  This  plant 
progressed  gradually  and  developed  into  the  American  Ce- 
ment Co.,  now  a  large  producer  of  both  natural  and  Portland  ce- 
cent.  From  this  time  on  plants  sprung  up  rapidly  in  the  Lehigh 
Valley  Section,  among  the  older  ones  being  the  Atlas,  Bonneville, 
Alpha  and  Lawrence,  all  now  important  producers. 

In  other  sections  also,  successful  mills  were  built..  In  New 
York,  Thomas  Millen,  who  had  previously  built  a  works  in  In- 
diana, and  his  son,  Duane  Millen,  started  the  Empire  Portland 
Cement  Co.,  at  Warners,  Onondaga  Co.,  in  1886.  In  Ohio,  at 
Harper,  Logan  Co.,  the  Buckeye  Portland  Cement  Co.  put  in 
operation  their  plant  in  1889;  and  in  1890  the  Western  Portland 
Cement  Co.,  of  Yankton,  S.  D.,  began  to  make  Portland  cement. 

From  that  time  on  the  Portland  cement  industry  has  taken  rapid 
strides  and  plants  have  been  built  in  almost  every  part  of  the 
country.  The  process  of  manufacture  has  been  greatly  improved, 
resulting  in  a  considerable  lessening  of  the  cost  of  production. 

1  Cement  Age,  July,  1905,  contains  an  interesting  account  by  Mr.  Millen  himself  of  how 
he  came  to  go  into  the  manufacture  of  Portland  cement  at  South  Bend. 


DEVELOPMENT  OF  THE  INDUSTRY 


II 


American  Portland  cement  has  practically  displaced  the  imported 
article.  New  uses  have  been  found  for  Portland  cement  and  it 
is  coming  rapidly  to  the  front  as  a  material  of  construction.  The 
new  American  Association  of  Portland  Cement  Manufacturers 
formed  in  1902,  promises  to  do  wonders  for  the  industry  and  to 
the  end  of  showing  the  many  uses  to  which  Portland  may  be  ap- 
plied with  advantage,  erected  a  building  and  prepared  an  exhibit 
for  the  Louisiana  Purchase  Exposition  at  St.  Louis  during  1904. 
Tables  III,  IV  and  V  show  the  growth  of  the  American  Port- 
land Cement  industry  and  Table  VI  gives  a  graphic  comparison 
of  the  imports,  production  and  consumption  of  Portland  and 
Natural  cements  from  1890  to  1903. 

TABLE   III.— TOTAL    PRODUCTION    OF    PORTLAND    CEMENT   IN 

THE  UNITED  STATES,  1870  TO  1904. 

(Mineral  Resources  of  United  States.) 


Year. 

Barrels. 

Year. 

Barrels. 

Year. 

Barrels. 

1870  to  1880 

82,000 

1888 

250,000 

1896 

1,543,023 

1880 

42,000 

1889 

300,000 

I897 

2,677,775 

1881 

6o,OOO 

1890 

335,000 

1898 

3,692,284 

1882 

85,000 

1891 

454,813 

l899 

5,652,266 

1883 

90,000 

1892 

547,440 

1900 

8,482,020 

1884 

100,000 

1893 

590,652 

1901 

12,711,225 

1885 

150,000 

1894 

798,757 

1902 

17,230,644 

1886 

150,000 

1895 

990,324 

1903 

22,342,973 

1887 

250,000 

1904 

26,505,881 

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New  York  
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All  other  sections  

3 

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PORTLAND  CEMENT 


140 


120 


100 


60 


40 


PER  CAPITA  CONSUMPTION 
OF  CEMENT 
IN  THE  UNITED  STATES 
FROM  1850  TO  1903. 

fl902 

/ 

»1901 

/ 

/ 

/ 

•» 

^T~ 

1850  1860  1870  1880  1890  1900 

TOTAL  CONSUMPTION  AND  PRODUCTION 
OF  PORTLAND  CEMENT 

IN  THE  UNITED  STATES, 

AND  IMPORTS  INTO  STATES, 
FROM    1890  TO   1903,  INCLUSIVE. 


1890  1881  1892  1893  1894'  18W  1896  1897  1898  1899  1900  1901  1902  1903 


CHAPTER  IL 


THE  NATURE  AND  COMPOSITION  OF  PORTLAND 

CEMENT. 


Portland  cement  may  be  defined  as  "the  finely  pulverized  pro- 
duct resulting  from  the  calcination  to  incipient  fusion  of  an  inti- 
mate mixture  of  properly  proportioned  argillaceous  and  calcar- 
eous materials  and  to  which  no  addition  greater  than  3%  has 
been  made  subsequent  to  calcination1." 

When  the  fine  powder  is  mixed  with  water  chemical  action 
takes  place,  and  a  hard  mass  is  formed.  The  change  undergone 
by  the  cement  mortar  in  passing  from  the  plastic  to  the  solid  state 
is  termed  "setting."  This  usually  requires  but  a  few  hours  at 
most.  On  completion  of  the  set  a  gradual  increase  in  cohesive 
strength  is  experienced  by  the  mass  for  some  time,  and  the  cement 
is  said  to  "harden."  Cements  usually  require  from  six  months  to 
a  year  to  gain  their  full  strength.  Cement  differs  from  lime  in 
that  it  hardens  while  wet  and  does  not  depend  upon  the  carbon 
dioxide  of  the  air  for  its  hardening.  It  is  very  insoluble  in  water 
and  is  adapted  to  use  in  moist  places  or  under  water  where  lime 
mortar  would  be  useless.  On  pages  16  and  17  are  two  tables 
showing  the  analysis  of  various  Portland  cements. 
Composition  of  Cement. 

Portland  cement,  according  to  Le  Chatelier,2  consists  of  a  mix- 
ture of  tricalcium  silicate,  3CaO.SiO2,  and  tricalcium  aluminate, 
3CaO.Al2O3.  He  arrived  at  this  conclusion  after  a  long  series  of 
experiments,  which  consisted  in  examining  thin  sections  of  ce- 
ment clinker  under  the  polarizing  microscope.  He  also  made  ex- 
periments upon  the  synthetic  production  of  calcium  silicates  and 
aluminates  by  heating  intimate  mixtures  of  finely  pulverized  sil- 
ica, alumina,  and  lime.  He  then  examined  into  the  hydraulic  prop- 
erties of  the  compounds  so  prepared.  He,  however,  failed  to  pre- 
pare the  tricalcium  silicate  directly  by  heating  lime  and  silica,  the 

1  Standard  Specifications,  Amer.  Soc.  Test.  Mat. 

2  Constitution  of  Hydraulic  Mortars,  (Trans,  by  Mack),  and  Annales  des  Mines,  1887, 
P- 345- 


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1 8  PORTLAND  CEMENT 

result  of  the  attempt  being  a  mixture  of  lower  silicates  and  lime, 
but  gave  it  as  his  opinion  that  this  compound  could  be  prepared 
indirectly  by  heating  together  a  mixture  of  fusible  silicates  and 
lime. 

The  tricalcium  silicate  is  the  essential  element  of  Portland  ce- 
ment, in  which  it  occurs  in  cubical  crystals.  In  this  compound 
the  lime  and  silica  bear  the  ratio  of  168 160.4  or  2.78  :i.  From  an 
analysis  of  Tiel  "Grappiers"  made  by  Hauenschild1,  it  will  be 
seen  that  they  are  approximately  pure  tricalcium  silicate. 

ANALYSIS  OF  TIEI,  "GRAPPIERS." 

Per  cent. 

Silica 23.6 

Lime 64.7 

Alumina 1.4 

Ferric  oxide 0.8 

Magnesia 1.4 

Sulphuric  anhydride 0.5 

Water 7.6 

100.0 

Ratio  of  lime  to  silica .' 2.74  :  i 

Theory  of  the  Hardening  of  Cement. 

Le  Chatelier  also  examined  thin  sections  of  hardened  cement 
under  the  microscope  and  found  that  it  consisted  of  hexagonal 
plates  of  crystallized  calcium  hydroxide,  Ca(OH)(2,  embedded  in 
a  white  matrix  of  interlaced  needle-shaped  crystals  of  hydrated 
monocalcium  silicate,  (CaSiO3,)2.5H2O.  From  these  researches 
he  concluded  that  the  tricalcium  silicate  when  mixed  with  water 
reacts  to  form  a  hydrated  monocalcium  silicate  and  calcium  hy- 
droxide according  to  the  reaction, 

2Ca3Si05  +  9H20  =  (CaSi03)2.5H20  +  4Ca(OH)2. 

The  calcium  hydroxide  then  probably  reacts  further  upon  the 
calcium  aluminate  of  the  cement,  forming  hydrated  basic  calcium 
aluminate,  Ca4 A12O7 . 1 2H2O. 

Ca3Al2O6  +  Ca(OH)2  +  nE^O  =  Ca4Al2OT.i2H,2O 
The  "hardening"  of  cements  is  due  to  the  first  reaction,  but  the 

i  Thonindustrie  Zeitung,  1883,  p.  418. 


COMPOSITION  OF  PORTLAND  CEMENT  IQ 

formation  of  the  hydrated'  basic  calcium  aluminate  probably  ex- 
erts a  marked  influence  upon  the  "setting"  properties  of  the  ce- 
ment. 

Hydraulic  Index. 

Assuming  that  three  molecules  of  lime  are  united  to  one  of  sil- 
ica to  form  the  tricalcium  silicate,  that  three  molecules  of  lime  are 
united  to  one  of  alumina  to  form  the  tricalciura  aluminate,  and 
that  these  two  compounds  are  the  essential  ingredients  of  cement, 
Le  Chatelier  gives  the  following  as  the  ratio  between  the  lime  and 
magnesia,  the  basic  elements,  and  the  silica  and  alumina,  the  acid 
elements  in  a  good  cement 

CaO  +  MgO< 


Si02 
and 


CaO  +  MgO         > 
Si02  —  A12Q3  —  FeA= 

Le  Chatelier  also  states  that  (  i  )  usually  gives  for  a  good  cement 
from  2.5  to  2.7,  and  (2)  from  3.5  to  4. 

This  ratio  betwen  the  silica  and  alumina  on  the  one  hand  and 
the  lime  on  the  other  is  termed  "hydraulic  index!' 

Erdmenger1  has  pointed  out,  however,  that  the  above  equations 
are  not  borne  out  by  experience,  as  the  assumption  that  lime  and 
magnesia  are  of  equal  hydraulic  value  is  an  error. 

Messrs.  Newberry's  Theories. 

Messrs.  Spencer  B.  and  W.  B.  Newberry1,  in  a  series  of  re- 
searches as  to  the  constitution  of  cement,  arrived  at  conclusions 
quite  different  from  those  of  Le  Chatelier.  They  prepared  sili- 
cates and  aluminates  of  lime  synthetically  by  heating  together  in 
a  Fletcher  gas  furnace  intimate  mixtures  of  finely  pulverized 
quartz  and  calcium  carbonate,  and  alumina  and  calcium  carbonate 
in  different  molecular  proportions.  They  then  examined  into  the 
hardening  and  setting  properties  of  the  resulting  compounds. 
While  these  chemists  agreed  with  Le  Chatelier  that  the  silica  in 
cement  is  present  as  tricalcium  silicate,  and  that  to  this  is  due  the 
ultimate  hardening  of  cement,  they  found  no  difficulty  in  prepar- 

1  J.  Soc.  Chein.  Ind.,  n,  1035. 


2O  PORTLAND  CEMENT 

ing  the  tricalcium  silicate  directly,  by  heating  together  silica  and 
lime  in  the  molecular  proportion  of  i  to  3.  The  Messrs.  New- 
berry,  however,  from  their  experiments  upon  the  calcium  alum- 
inates  concluded  that  the  alumina  is  in  combination  with  the  lime 
as  dicalcium  aluminate  and  not  as  tricalcium  aluminate.  Their 
experiments  led  them  to  the  following  conclusions : 

"First. — Lime  may  be  combined  with  silica  in  the  proportion 
of  3  molecules  to  I,  and  still  give  a  product  of  practically  constant 
volume  and  good  hardening  properties,  though  hardening  very 
slowly.  With  3^  molecules  of  lime  to  i  of  silica  the  product  is 
not  sound,  and  cracks  in  water. 

"Second. — Lime  may  be  combined  with  alumina  in  the  propor- 
tion of  2  molecules  to  I,  giving  a  product  which  sets  quickly,  but 
shows  constant  volume  and  good  hardening  properties.    With  2^2 
molecules  of  lime  to  I  of  alumina  the  product  is  not  sound." 
Newberry's  Formula. 

The  formula  for  the  tricalcium  silicate,  3CaO.SiO2,  corre- 
sponds to  2.8  parts  by  weight  of  lime  to  i  part  of  silica,  and  the 
formula  for  the  dicalcium  aluminate,  2CaO.Al2O3,  corresponds 
to  i.i  parts  of  lime  to  I  of  alumina.  From  this  the  following 
formula  is  given  as  representing  the  maximum  of  lime  which 
should  be  present  in  a  correctly  balanced  Portland  cement;  per 
cent  lime  =  per  cent  silica  X  2.8  +  per  cent  alumina  X  i.i. 

They  found  that  cement  prepared  synthetically  with  lime, 
alumina,  and  silica  proportioned  according  to  the  above  formula 
gave  good  results,  whereas  that  prepared  by  Le  Chatelier's  form- 
ula was  unsound,  showing  the  lime  to  be  in  excess. 

Tornebohm' s  Investigations. 

Tornebohm,1  a  Sweedish  investigator,  checked  the  microscopic 
work  of  Le  Chatelier  and  identified  in  Portland  cement  four  dis- 
tinct mineral  constituents  which  he  called  Alit,  Belit,  Felit  and 
Celit,  and  described  as  follows2: — 

"Alit  is  the  preponderating  element  and  consists  of  colorless 
crystals  of  rather  strong  refractive  power,  but  of  weak  double  re- 
fraction. By  this  he  means  that  Alit  in  polarized  light  between 

1  Kongreb  des  intern  verb,  fur  material  priiff  Stokholm,  1897. 

2  Richardson,  Papers  Asso.  Port.  Cem.  Mfgs.,  June  15,  1904. 


COMPOSITION  OF  PORTLAND  CEMENT  21 

crossed  Nicol  prisms  has  insufficient  optical  activity  to  produce 
more  than  weak  interference  colors  of  a  bluish  gray  order. 

"Celit  is  recognized  by  its  deep  color,  brownish  orange.  It  fills 
the  interstices  between  the  other  constituents  and  eventually 
forms  the  magma  or  liquid  of  lowest  freezing  point  out  of  which 
the  Alit  is  separated.  It  is  strongly  double  refractive,  that  is  to 
say,  gives  brilliant  colors  when  examined  between  crossed  Nicol 
prisms. 

"Belit  is  recognized  by  its  dirty  green  and  somewhat  muddy 
color  and  by  its  brilliant  interference  colors.  It  is  bi-axial  and  of 
high  index  of  refraction.  It  forms  small  round  grains  of  no  rec- 
ognized crystalline  character. 

"Felit  is  colorless.  Its  index  of  refraction  is  nearly  the  same  as 
that  of  Belit  and  it  is  strongly  double  refractive.  It  occurs  in  the 
form  of  round  grains,  often  in  elongated  form,  but  without  crys- 
talline outline.  Felit  may  be  entirely  wanting. 

"Besides  these  minerals  an  amorphous  isotropic  mass  was  de- 
tected by  Tornebohm  and  Le  Chatelier.  It  is  called  isotropic  be- 
cause it  has  no  effect  upon  polarized  light.  It  has  a  very  high  re- 
fractive index. 

"Tornebohm  adds  the  important  fact  that  a  cement  4%  richer 
in  lime  than  usual  consists  almost  entirely  of  Alit  and  Celit." 

Richardson's  Work. 

Clifford  Richardson,  an  American  chemist,  in  a  paper,  read  be- 
fore the  Association  of  Portland  Cement  Manufacturers  at  At- 
lantic City,  N.  J.,  June  15,  1905,  described  the  results  of  a  thor- 
ough and  exhaustive  microscopic  study  of  Portland  cement  clink- 
er. As  the  result  of  this  investigation  he  again  advanced  the 
theory  first  brought  forward  by  Winkler1  in  1858,  I  believe,  that 
Portland  cement  clinker  is  a  solid  solution.  This  paper  is  by  far  the 
most  valuable  argument,  so  far  advanced,  explaining  the  proper- 
ties of  cement  along  the  lines  of  physical  chemistry,  and  the  in- 
vestigations which  led  up  to  it,  the  most  thorough  so  far  under- 
taken. Richardson  prepared  many  synthetic  silicates  and  alum- 
inates  and  determined  their  optical  properties,  hydraulic  value 
and  phyiscal  characteristics.  These  he  describes  as  follows : — 

i  Dingier" spolyt.  Jour.,  CI.XXV,  p.  208. 


22  PORTLAND  CEMENT 

"Mono-calcic  silicate-  SiO2CaO :  A  crystalline  substance  of 
high  optical  activity  and  little  or  no  hydraulic  properties.  Spe- 
cific gravity  2.9. 

"Di-calcic  silicate-  SiO2CaO,  or  more  probably  2SiO24CaO :  A 
definite  crystalline  compound  of  high  optical  activity  and  of  very 
little  hydraulic  activity  except  in  the  presence  of  carbonic  acid, 
but  setting  slowly  in  water,  generally  lacking  volume  constancy. 
Specific  gravity  3.29. 

"Tri-calcic  silicate-  SiO23CaO,  or  more  probably  2SiO26CaO : 
A  definite  crystalline  silicate  of  low  optical  activity  and  corre- 
sponding in  this  respect  with  Alit.  Its  hydraulic  activity  is  not 
great  but  greater  than  that  of  di-calcic  silicate.  If  fused  and  re- 
ground  it  sets  slowly  like  Portland  cement.  Specific  gravity  3.03. 

"Three  definite  silicates  of  calcium,  therefore,  exist,  the  two 
more  basic  ones  being  strongly  differentiated  from  each  other  by 
their  optical  activity. 

"Mono-calcic  aluminate-  Al2O3CaO :  This  aluminate  is  a  crys- 
talline substance  of  high  optical  activity,  but  it  is  not  sufficiently 
basic  to  be  found  in  a  material  of  such  basic  character  as  Port- 
land cement  clinker.  Specific  gravity  2.90. 

"Tri-calcic  di-aluminate-  2Al2O33CaO :  This  aluminate  is  one 
of  highly  crystalline  character  and  of  great  optical  activity,  mak- 
ing it  readily  recognizable.  Specific  gravity  2.92. 

"Di-calcic  aluminate-  Al2O32CaO :  A  substance  crystallizing 
from  a  state  of  fusion  in  dendritic  forms  having  no  optical  ac- 
tivity and  being,  therefore,  isotropic.  This  differentiates  this 
aluminate  very  sharply  from  the  preceding  one  and  makes  the 
identification  of  the  two  materials  very  easy.  Specific  gravity 
2.79. 

"Tri-calcic  aluminate-  Al2O33CaO :  This  aluminate  crystallizes 
from  the  fused  condition  in  elongated  octa-hedra.  It  is  isotropic 
and  it  might  at  first  be  assumed  that  it  was  not  a  definite  com- 
pound, but  merely  the  di-calcic  silicate  crystallizing  out  of  a  mag- 
ma of  indefinite  composition.  It  has  been  shown,  however,  by 
further  investigations  too  lengthy  to  go  into  at  this  point  to  be 
undoubtedly  a  .definite  aluminate.  Specific  gravity  2.91." 


COMPOSITION  OF  PORTLAND  CEMENT  23 

Solid  Solution  Theory. 

Richardson  following  the  supposition  that  clinker  is  a  solid  so- 
lution, prepared  clinkers  of  pure  silica,  alumina  and  lime,  in  the 
proportions  met  with  in  the  industrial  product.  The  proper  mole- 
cular proportions  were  obtained  by  calculation  from  two  very 
exact  analyses  of  industrial  clinker,  just  as  is  done  in  calculating 
the  formula  of  a  mineral,  and  the  ratio  6  to  I  was  chosen  as  rep- 
resentative of  practical  manufacturing  conditions.  Clinkers  hav- 
ing the  following  formulae  were  then  prepared : — 

!2(Si02  3CaO)  +  2(A1203  CaO)  =  38  CaO 

"      +  i  ( 2 A1203  3CaO )  =  39  CaO 
"      -f  2(A12O3  2CaO)  =40  CaO 
"      -f  2(A12O3  3CaO)  =•  42  CaO 

"Thin  sections  of  these  clinkers  showed  that  the  one  corre- 
sponding to  the  substance  present  as  mono-calcic  aluminate  con- 
tained a  very  considerable  amount  of  Celit,  that  corresponding  to 
the  next  higher  degree  of  basicity,  2Al2O33CaO,  contained  less, 
that  corresponding  to  Al2O32CaO  still  less,  while  that  in  which 
tri-calcic  aluminate,  Al2O33CaO,  is  supposed  to  be  the  form  in 
which  the  aluminate  is  present  contains  no  Celit,  but  is  a  pure  Alit 
corresponding  in  every  way  with  that  seen  in  industrial  Portland 
cement  clinker. 

"The  composition  of  Alit  is,  in  this  way,  entirely  satisfac- 
torily explained.  It  is  a  solid  solution  of  tri-calcic  silicate 
in  tri-calcic  aluminate.  And  on  reflection  it  is  readily  seen 
that  the  di-calcic  aluminaterfcould  not  become  dissolved  in  tri- 
calcic  silicate  without  reaction  going  on  and  an  interchange 
of  base  between  the  tri-calcic  silicate  and  di-calcic  alum- 
inate to  such  an  extent  as  to  convert  a  portion  of  the 
di-calcic  aluminate  to  the  tri-calcic  form  and  a  corre- 
sponding portion  of  the  tri-calcic  silicate  to  the  di-calcic 
form.  The  tri-calcic  aluminate  then  dissolves  in  the  tri-calcic 
silicate  and  the  di-calcic  aluminate  in  the  di-calcic  silicate,  thus 
forming  two  separate  and  distinct  solid  solutions,  the  one  Alit  and 
other  Celit,  which,  while  no  doubt  miscible  in  the  molten  condi- 
tion, are  not  so  in  the  solid  form.  In  the  same  way  the  inter- 
change of  bases  in  the  clinkers  of  less  basic  form  where  the 


24  PORTLAND  CEMENT 

amount  of  lime  was  only  sufficient  to  account  for  the  presence  of 
mono-calcic  or  tri-calcic  di-aluminate,  would  result  in  a  similar 
state  of  affairs,  but  with  a  much  larger  percentage  of  Celit  as  the 
basicity  decreases." 

Richardson  also  concludes1  that  the  setting  of  Portland  cement 
is  almost  entirely  due  to  the  decomposition  of  the  Alit,  examina- 
tion showing  the  Celit  to  be  almost  unattacked;  and  that  the 
strength  of  Portland  cement  after  setting  is  due  entirely  to  the 
crystallization  of  calcium  hydrate  under  certain  favorable  condi- 
tions, and  not  at  all  to  the  hydration  of  the  silicates  and  alumi- 
nates.  His  theory  is  that  "on  addition  of  water  to  the  stable  sys- 
tem made  up  of  the  solid  solutions  which  compose  Portland  ce- 
ment, a  new  component  is  introduced,  which  immediately  results 
in  lack  of  equilibrium,  which  is  only  brought  about  again  by  the 
liberation  of  free  lime.  This  free  lime  the  moment  that  it  is  lib- 
erated, is  in  solution  in  the  water,  but  owing  to  the  rapidity  with 
which  it  is  liberated  from  the  aluminate,  the  water  soon  becomes 
supersaturated  with  calcic  hydrate  and  the  latter  crystallizes  out 
in  a  network  of  crystals,  which  binds  the  particles  of  undecom- 
posed  Portland  cement  together."  The  initial  set  is  due  to  the 
aluminates,  while  subsequent  hardening  is  due  to  the  slower  lib- 
eration of  lime  from  the  silicates.  ^ 

Substances  Found  in  Cement. 

All  these  investigators  agree  that  the  essential  ingredients  of 
Portland  cement  are  lime,  silica,  and  alumina.  A  little  of  the 
alumina  is  always  replaced  by  ferric  oxide  and  some  of  the  lime 
by  magnesia.  Small  percentages  of  alkalies,  potash  and  soda, 
present  in  the  clay  as  silicates,  are  also  in  cement,  while  the  most 
thorough  burning  fails  to  drive  off  all  the  carbon  dioxide  from  the 
limestone  or  marl  in  the  raw  mixture,  leaving  a  trace  in  the  finish- 
ed product.  This  trace  is  increased  by  the  absorption  of  this  con- 
stituent from  the  atmosphere.  Water  is  also  absorbed  from  the 
air  and  traces  of  manganese,  titanium,  phosphorus,  strontium,  fer- 
rous oxide  and  sulphides  are  usually  present  in  Portland  cement. 
In  analyzing  cement  it  is  generally  sufficient  to  know  the  silica, 
lime,  alumina  and  ferric  oxide  together,  and  the  magnesia;  less 

1  Papers  Association  of  Portland  Cement  Manufacturers,  Dec.  14,  1904. 


COMPOSITION  OF  PORTLAND  CEMENT  25 

often  the  alumina  and  ferric  oxide  separately,  the  sulphuric  acid 
and  the  carbon  dioxide,  while  more  rarely  yet  the  alkalies,  com- 
bined water,  and  the  sulphur  present  as  sulphate  and  sulphide  re- 
spectively. 

Lime. 

A  good  cement  contains  from  58  to  67  per  cent  lime,  the 
amount  depending  upon  the  relative  proportions  of  silica  and 
alumina,  and  also  upon  the  care  with  which  the  cement  has  been 
manufactured.  Up  to  the  limit,  it  may  be  said,  that  the  more  lime 
that  is  present  in  a  cement  the  greater  will  be  its  strength.  The 
limit  is  reached,  however,  when  more  lime  is  present  than  will 
combine  chemically  with  the  silica  and  alumina,  leaving  some 
lime  in  the  uncombined  state.  Lime  in  slaking  expands  so  that 
an  excess  of  lime  over  what  will  unite  with  the  silica  and  alumina 
will  cause  the  cement  to  expand,  -or  "blow"  as  it  is  technically 
termed]  and  crack. 

High  lime  cements  are  usually  very  slow  setting,  but  harden 
rapidly,  sometimes  reaching  their  maximum  strength  in  28  days. 
After  this  time,  retrogression  apparently  takes  place  in  the 
strength  of  neat  test  pieces  subjected  to  tension  and  much  discus- 
sion has  taken  place  as  to  whether  this  is  due  to  internal  disrup- 
tion of  the  briquettes  or  merely  to  the  fact  that  the  increasing 
hardness  has  made  them  brittle,  and  consequently  likely  to  be 
fractured  by  the  distortion  met  with  in  breaking  such  a  short 
piece  rather  than  to  the  tensile  stress  applied.  This  latter  theory 
seems  to  be  the  true  one,  as  compression  specimens  seldom  show 
such  retrogression  at  longer  periods.  The  sand  briquettes  also 
usually  show  some  increase  of  strength  with  time,  even  when  the 
neat  ones  fail.  Provided  a  cement  is  sound,  there  is  nothing  in 
the  theory  that  cements  which  harden  slowly  and  show  progress- 
ive gain  are  any  better  than  those  which  harden  promptly,  and  a 
cement  which  reaches  its  maximum  strength  promptly  would 
seem  to  anyone  who  gives  the  matter  consideration  much  more 
desirable  than  one  which  takes  several  years  to  reach  the  same 
point. 

Cements  low  in  lime  usually  contain  clay  in  excess,  for  suffi- 
cient lime  was  not  originally  present  in  the  raw  material  to  change 


26  PORTLAND  CEMENT 

all  the  clay  to  silicates  and  aluminates.  This  excess  of  clay,  of 
course,  is  devoid  of  cementing  qualities  and  may  be  looked  upon 
as  just  so  much  foreign  matter.  Though  it  will  not  cause  the 
cement  to  fall  to  pieces  subsequently,  it  takes  away  from  its 
strength  because  in  its  place  should  be  cement.  Low  lime  ce- 
ments are  apt  to  be  "quick  setting."  Hence,  one  of  the  remedies 
for  "quick  setting"  cement  is  to  increase  the  lime  content  of  the 
raw  mixture.  For  this  reason  high  alumina  cements  often  con- 
tain more  lime  than  those  low  in  alumina,  in  spite  of  the  fact  that 
alumina  combines  with  less  lime  than  does  silica. 

The  amount  of  lime  a  cement  will  bear  depends  upon  the 
care  with  which  the  mixture  of  raw  materials  is  made.  Thus 
poorly  ground,  imperfectly  mixed  raw  materials  would  probably 
result  in  a  very  much  over-limed  cement,  if  the  lime  limit  (as 
shown  by  chemical  analysis  of  the  clay,  marl,  limestone  or  cement 
rock  of  the  mixture)  was  anywhere  near  reached ;  for  the  coarse 
particles  of  calcium  carbonate  would  not  come  into  sufficiently 
close  contact  with  the  silica  and  alumina  to  completely  combine 
with  the  latter.  A  properly  burned  cement  will  also  stand  a  great- 
er percentage  of  lime  than  an  improperly  burned  one.  A  cement 
in  which  the  temperature  at  burning  was  too  low  to  heat  all  the 
lime  to  the  point  of  combination  with  the  silica  and  alumina, 
would  naturally  contain  free  lime.  Chemical  analysis,  therefore, 
if  taken  alone  as  the  guide  to  a  cement,  will  seldom  tell  us  much 
where  the  lime  content  is  concerned ;  as  of  two  cements  contain- 
ing the  same  quantity  of  lime,  one  properly  made  might  be  quite 
sound  while  the  other,  from  faulty  mixing  and  burning,  might  be 
anything  but  sound. 

Most  of  the  Portland  cements  made  in  the  United  States,  in  the 
rotary  kiln,  contain  when  freshly  ground  between  61  and  64  per 
cent  lime,  with  about  63  per  cent  for  an  average.  Cement  after 
standing  of  course  contains  much  less  lime  than  this  because  the 
absorption  of  water  and  carbon  dioxide  lowers  the  percentage  of 
lime.  The  percentage  of  lime  to  be  carried  at  any  works  is 
usually  controlled  by  two  things,  the  "setting  time"  and  the 
"soundness."  There  must  be  enough  lime  present  to  keep  the  ce- 
ment from  being  quick  setting,  either  when  made  or  after  season- 
ing, and  there  must  not  be  so  much  lime  present  that  the  cement 


COMPOSITION  OF  PORTLAND  CEMENT  2.J 

will  fail  on  the  soundness  test.  With  raw  materials  high  in  alum- 
ina, the  margin  between  the  maximum  and  minimum  limits  is 
small.  With  such  materials  extreme  care  is  needed  in  the  process 
of  manufacture  and  the  raw  materials  should  be  very  finely 
ground,  and  the  burning  thorough.  When  the  alumina  is  low  the 
margin  is  much  greater,  but,  if  the  lime  is  carried  near  the  max- 
imum, a  stronger  cement  will  result. 

Silica. 

Silica  is,  of  course,  next  to  lime  the  most  important  constituent 
of  Portland  cement  and  present  in  the  next  largest  proportion. 
Portland  cements  usually  contain  from  19  to  .25  per  cent  silica. 
Those  containing  the  latter  figure  are  usually  low  in  alumina  and 
those  containing  the  former  are  high  in  alumina.  High  silica 
cements  are  usually  slow  setting  and  of  good  tensile  strength.  In- 
creasing the  silica  usually  increases  both  the  strength  and  setting 
time.  It  increases  the  temperture  of  burning,  also,  however.  Ce- 
ment should  contain  at  least  2.5  times  as  much  silica  as  alumina 
in  order  to  prevent  its  being  quick  setting.  Since  the  silicates 
available  for  cement  manufacture  usually  contain  too  much  alum- 
ina for  this  proportion,  clays,  containing  some  free  or  uncombined 
silica  are  the  source  of  the  silica  in  cement.  In  increasing  the  sil- 
ica in  the  unburned  cement,  mixture,  therefore,  clays  having  this 
free  silica  in  such  a  fine  state  of  subdivision,  that  it  may  easily 
combine  with  the  lime,  must  be  selected  and  not  clays  in  which 
the  free  silica  is  present  as  quartz,  pebbles,  etc.  For  the  same 
reason  the  silica  in  cement  can  never  be  increased  by  the  addition 
of  quartz  or  flint  to  the  raw  materials,  but  instead  another  and 
more  silicious  clay,  shale  or  cement  rock  must  be  found  and  used 
in  place  of,  or  mixed  with  the  high  alumina,  clay,  etc. 

Alumina. 

Portland  cement  usually  contains  between  5  and  10  per  cent 
alumina.  As  the  percentage  of  alumina  rises,  the  cement  becomes 
more  quick-setting.  When  the  percentage  of  alumina  rises  above 
10  per  cent  the  cement  becomes  very  quick-setting,  with  a  corre- 
sponding decrease  of  tensile  strength.  This  is  to  be  expected, 
since  the  strength  of  cement  is  due  to  the  calcium  silicate,  and  its 


28  PORTLAND  CEMENT 

setting  properties  to  the  calcium  aluminate.  As  the  calcium 
aluminate  is  very  fusible,  the  clinkers  obtained  on  burning  mix- 
tures high  in  alumina  are  very  fusible,  hard  to  burn  uniformly  and 
difficult  to  grind.  Cement  clinkers  made  from  kaolin  show  all  of 
these  properties  and  the  finished  cement  is  low  in  tensile  strength. 

Ferric  Oxide. 

According  to  Le  Chatelier,  ferric  oxide  and  calcium  carbonate 
on  burning  yield  products  which  slake  with  water  and  possess  no 
hydraulic  properties.  Schott,  however,  prepared  cement  contain- 
ing only  lime,  silica  and  ferric  oxide,  which  showed  excellent 
hardening  qualities,  and  therefore  concluded  that  alumina  could 
be  completely  replaced  by  ferric  oxide  without  diminishing  in  any 
way  the  hydraulic  properties  of  cement.  S.  B.  and  W.  B.  New- 
berry  from  their  researches  concluded  that  ferric  oxide  and  alum- 
ina act  in  a  similar  manner  in  promoting  the  combination  of  silica 
and  lime. 

Zulkowsky  also  made  experiments  along  this  line  and  his  con- 
clusions agree  with  those  of  Schott  and  Newberry,  and  it  is  now 
generally  agreed  that  the  iron  oxide  in  the  cement  mixture  acts  as 
a  flux  and  promotes  the  combination  of  the  silica  and  the  lime. 
Mixtures  of  silica,  alumina,  and  lime,  in  the  proportions  usually 
found  in  cement,  are  extremely  hard  to  burn.  The  replacement 
of  part  of  the  alumina  by  iron,  however,  greatly  lowers  the  tem- 
perature of  burning.  One  of  the  cures  for  unsound  cement  is 
therefore  found  in  the  replacement  of  clays  high  in  alumina  by 
those  high  in  iron.  As  iron  does  not  seem  to  make  cement  quick- 
setting,  iron  may  be  made  to  replace  alumina  to  advantage  in 
many  instances.  In  mixtures  high  in  silica  and  consequently  hard 
to  burn,  the  addition  of  some  soft  iron  ore,  such  as  brown  hema- 
tite, to  the  mix  should  lower  the  temperature  at  which  clinkering 
takes  place  and  make  it  easier  to  produce  a  sound  cement. 

Of  late  years  numerous  authorities  have  come  forward  advo- 
cating Portland  cement  containing  high  percentages  of  ferric  ox- 
ide for  use  in  sea  water,  claiming  for  such  cements  great  resist- 
ance to  the  disintegrating  influence  of  the  salts  of  magnesium, 
etc.,  found  in  sea  water.  This  claim  seems  well  backed  by  ex- 
periments and  theory  and  deserves  a  thorough  investigation. 


COMPOSITION  OF  PORTLAND  CEMENT  2Q 

The  amount  of  ferric  oxide  in  cements  is  usually  small,  less 
than  5  per  cent.  The  dark  gray  color  of  cement  is  due  to  the 
presence  of  iron  compounds.  Cement  prepared  from  silica,  lime, 
and  alumina  only  is  colorless,  but  upon  replacing  the  alumina  by 
ferric  oxide  the  cement  becomes  gray. 

Magnesia. 

A  cement  containing  iV2  per  cent  of  magnesia  was  long  con- 
sidered dangerous ;  now  4  per  cent  in  cement  is  thought  to  be 
harmless,  and  many  authorities  allow  even  5  per  cent  magnesia. 
The  popular  supposition  is  that  magnesia  in  considerable  percent- 
ages causes  cement  in  time  to  expand  and  crack.  R.  Dykerhoff 
presented  to  the  German  Association  of  Cement  Manufacturers 
in  1895  the  results  of  a  very  thorough  research  into  the  effects  of 
magnesia.  From  his  experiments  he  concluded  that  magnesia, 
whether  added  to  a  normal  mixture  or  substituted  for  an  equiva- 
lent portion  of  lime,  causes  a  decrease  of  strength  in  the  resulting 
cement,  when  present  in  more  than  4  per  cent.  Cracking  only  oc- 
curred with  8  per  cent  or  more  magnesia.  A  commission  from 
the  American  Association  is  now  studying  the  effects  of  magne- 
sia. I/e  Chatelier  in  his  formula  considers  magnesia  to  replace 
lime,  while  the  Newberrys  in  their  formula  consider  it  inactive 
and  not  to  replace  lime. 

Authorities  differ  as  to  the  hydraulic  values  of  magnesium  sili- 
cates. Fuch,  Ueven,  Rivot,  Kawalewsky,  and  Zulkowski  all  pre- 
pared magnesium  cements,  while  S.  B.  and  W.  B.  Newberry  and 
Held  were  not  able  to  prepare  compounds  of  any  hydraulic  value 
from  magnesia.  It  is  probable,  however,  that  if  these  magnesian 
silicates  have  any  real  hydraulic  value  they  are  at  least  inferior  to 
the  lime  silicates  and  hence  magnesia  may  be  considered  a  disad- 
vantage in  cement,  in  that  it  takes  the  place  of  a  more  active  and 
important  lime  compound.  Whether  magnesia  should  be  consid- 
ered in  calculating  cement  mixtures  is  also  a  debated  point,  and 
one  with  which  the  hydraulic  value  of  the  magnesian  compounds 
has  nothing  to  do,  as  the  question  is  simply  whether  or  not  the 
magnesia  is  combined  with  silica  and  alumina  in  cement.  If  it 
does  combine,  enough  of  the  silica  and  alumina  should  be  present, 
not  only  to  form  the  proper  lime  compounds,  but  also  the  proper 


3O  PORTLAND  CEMENT 

magnesian  compound,  or  else  the  cement  will  be  too  basic  and 
will  probably  contain  an  excess  of  uncombined  lime. 

The  standard  specifications  place  the  maximum  amount  of  mag- 
nesia (MgO)  allowable  in  a  Portland  cement  at  4  per  cent. 

Alkalies. 

Potash  and  soda  are  present  in  all  cements  in  small  quantities, 
usually  less  than  0.75.  A  large  proportion  of  the  alkalies  present 
in  the  raw  material  are  driven  off  in  burning.  Experiments  made 
by  the  writer  with  the  cement  rock  of  the  Lehigh  Valley  indicate 
that  at  least  one-half  the  potash  is  lost  in  the  kiln,  passing  off  in 
the  kiln  gases.  The  loss  of  soda  is,  of  course,  much  less  since  this 
is  the  less  volatile  of  the  two  alkalies.  It  is  supposed  that  the 
alkalies  act  as  a  flux  and  promote  the  combination  of  the  silica  and 
the  alumina  with  the  lime,  and  experiments  made  by  the  writer 
with  small  kilns  certainly  confirm  this  theory. 

The  addition  of  small  quantities  of  either  the  carbonates  or  the 
hydroxides  of  potash  and  soda  will  cause  cement  to  set  quickly, 
and  it  is  probable  that  the  presence  of  any  considerable  quantity 
of  alkali  in  cement  would  cause  it  to  set  quickly.  When  quick 
setting  cement  is  due  to  the  presence  of  the  alkalies,  the  trouble 
can  be  remedied,  to  some  extent,  by  raising  the  temperature  of 
burning,  thus  volatilizing  the  alkali.  Cements  made  from  alkali 
waste  often  contain  large  quantities  of  potash  and  soda,  in  some 
cases  the-  amount  reaching  as  high  as  2.5  per  cent.  Butler1  states. 
that  instances  have  occurred  in  which  these  cements  gave  any- 
thing but  satisfactory  results,  and  the  only  fault  that  could  be 
found  with  their  chemical  composition  was  a  slight  excess  of 
alkali.  In  most  cement  the  alkalies  are  present  in  such  small 
quantities  that  their  effects  are  of  little  hydraulic  importance. 

Sulphur. 

Several  compounds  of  sulphur  are  present  in  cement ;  chief  of 
these  are  calcium  sulphate  and  calcium  sulphide.  The  action  of 
calcium  sulphate  upon  cement  is  to  delay  the  set.  For  this  reason 
it  is  always  added  in  the  form  of  gypsum  or  plaster  of  Paris  to  the 
cement  after  burning.  The  standard  specifications  so  far  recog- 
nize the  necessity  for  the  addition  as  to  allow  manufacturers  to 

1  Portland  Cements,  by  R.  D.  Butler,  p.  263. 


COMPOSITION  OF  PORTLAND  C£M£NT  31 

employ  a  proportion  not  exceeding  3  per  cent,  in  order  to  confer 
to  the  cement,  slow-setting  properties.  Although  the  presence  of 
calcium  sulphate  in  small  quantities  is  beneficial  to  cement,  there 
is  no  doubt  that  a  quantity  exceeding  4  or  5  per  cent,  is  injurious. 
The  standard  specifications  allow  1-75%  sulphur  trioxide 
(SO3)  in  Portland  cement.  The  retrogression  often  met  with  in 
neat  Portland  cement  briquettes  is  often  attributed  to  the  presence 
of  calcium  sulphate  in  the  cement.  My  own  experiments,  how- 
ever, made  with  cements  to  which  no  gypsum  had  been  added,  and 
the  same  cement  «with  the  addition  of  2  per  cent,  gypsum,  do  not 
indicate  this,  as,  in  most  cases,  where  retrogression  occurred  in 
the  cement  to  which  sulphate  had  been  added,  it  also  occurred 
with  the  unsulphated  cement.  Sulphates  increase  the  strength  of 
cement,  and  if  they  are  present  in  larger  amounts  than  2  or  3  per 
cent.,  will  unquestionably  cause  higher  short  time  tests  than  the 
long  period  ones,  though  this  may  be  due  merely  to  the  test  pieces 
becoming  brittle.  The  presence  of  sulphates  in  cement  promotes 
soundness,  or  at  least  enables  some  cements  to  pass  the  acceler- 
ated tests.  The  property  of  gypsum  and  plaster  of  Paris  to  re- 
tard the  set  of  cement  is  touched  upon  to  greater  length  in  the 
section  on  "Setting  Time." 

Carbon  Dioxide  and  Water. 

Carbon  dioxide  and  water  are  present  in  all  cements,  the 
amount  usually  varying  with  the  age  of  the  cement.  Freshly- 
ground  cements  usually  show  less  than  I  per  cent,  of  these  two 
constituents  combined,  while  well-seasoned  ones  may  show  as 
much  as  3  or  4  per  cent.  Underburned  cements  may,  or  may  not, 
.show  high  loss  on  ignition.  It  is  possible  to  drive  off  all  the  car- 
bon dioxide  from  the  raw  material,  and  yet  not  bring  the  mass 
to  the  point  of  incipient  vitri^action  necessary  to  produce  a  sound 
•clinker.  Samples  of  underburned  clinker  will  frequently  show  a 
loss  on  ignition  (water  and  carbon  dioxide)  as  low  as  that  of 
well-burned  cement.  If  the  sample  is  left  in  the  air,  however,  it 
;soon  shows  a  very  high  loss  on  ignition,  due  to  absorption  of 
water  and  carbon  dioxide  from  the  air.  Some  of  the  water  pres- 
ent in  cement  can  be  driven  off  at  110°  C,  while  some  of  it  re- 
quires a  red  heat  for  its  expulsion.  Determinations  of  loss  on  ig- 


PORTLAND  CEMENT 


nition,  unless  very  high,  are,  as  a  rule,  of  little  help  in  determin- 
ing the  quality  of  cement,  since  an  amount  as  high  as  4  per  cent, 
may  be  due  to  "aging"  of  the  cement,  which  is  recognized  as 
beneficial  to  it.  The  standard  specifications  wisely  make  no  re- 
quirements as  to  the  maximum  limit  for  loss  on  ignition. 

Other  Compounds  in  Portland  Cement. 

Besides  the  compounds  mentioned  above,  cement  usually  con- 
tains small  amounts  of  Titanic  Acid,  Ti2O3;  Ferrous  Oxide, 
FeO;  Manganous  Oxide,  MnO;  Phosphorus  Pentoxide,  P2O5; 
and  Strontium  Oxide,  SrO.  It  is  doubtful  if  these  compounds 
have  any  effect  on  the  hydraulic  or  setting  properties  of  Portland 
cement  when  present  in  the  minute  quantities  usually  found  in 
commercial  cements.  It  is  probable  that  titanic  acid  can  be  sub- 
stituted for  silica,  but  this  cement  would  be  hard  to  burn;  Man- 
ganese Oxide  acts  as  a  flux  and  cements  have  been  made  in  which 
Strontium  replaced  lime. 

The  author  found  in  three  Portland  cements  from  the  Lehigh 
District  the  amounts  of  the  rarer  constituents  stated  below : 


Cement  No. 

I                          2                          3 

0.28 
0.23 
0.06 
0.08 
0.18 
0.50 
0.26 
0.25 

0.27 
0.16 
0.08 

0.09 
0.48 
0.31 
0.31 

0.32 

O.I  I 

0.09 

0.07 

0-59 
0.38 
0.29 

MANUFACTURE. 


CHAPTER  III 


RAW  MATERIALS. 


Essential  Elements. 

As  we  have  seen  from  the  preceding  chapter  the  essential  ele- 
ments of  Portland  cement  are  silica,  SiO2,  alumina,  A12O3,  and 
lime,  CaO.  Silica  and  alumina  both  exist  pure  in  nature,  the  first 
as  quartz  and  flint  and  the  second  as  corundum  or  emery.  Neither 
quartz  nor  corundum  are  suitable  for  cement  making,  because 
of  their  extreme  hardness  and  the  impossibility  of  reducing  them 
to  the  degree  of  fineness  necessary  for  their  combining  with  the 
lime.  Silica  and  alumina,  however,  together  are  the  essentials  of 
clay  (or  shale)  and  this  is  the  source  of  these  elements  for  ce- 
ment manufacture.  Lime  is  not  found  free  in  nature,  but  com- 
bined with  carbon  dioxide  forms  calcium  carbonate,  CaCO3, 
which  occurs  in  many  parts  of  the  country  under  the  names  lime- 
stone, chalk  and  marl.  Most  limestones  contain  some  clay  and 
when  this  is  present  to  the  extent  of  18  or  more  per  cent,  what  is 
known  as  "cement  rock"  or  argillaceous  limestone  results.  Cer- 
tain by-products  of  other  industries  contain  one  or  more  of  the 
essential  elements  of  Portland  cement  in  a  condition,  and  in  pro- 
portions suitable  for  Portland  cement  manufacture.  In  this 
country,  blast  furnace  slag  is  now  used  and  caustic-soda  waste 
has  been  tried. 

Classification  of  Materials. 

Portland  cement  may  be  and  is  manufactured  from  a  variety  of 
raw  materials.  Those  used  may  be  classed  under  two  general 
head,  (i)  calcareous,  (2)  argillaceous,  according  as  the  lime  or 
the  silica  and  alumina  predominate. 

Calcareous.  Argillaceous. 

Limestone,  Clay, 

Marl,  Shale, 

Chalk,  Slate, 

Alkali  waste,  Blast-furnace  slag. 

Cement  rock.1 

i  Cement  rock  may  be  considered  as  either  calcareous  or  argillaceous.  Usually  it  may 
be  classed  as  the  latter,  but  in  the  neighborhood  of  Nazareth,  Pa.,  the  rock  in  several  places 
runs  so  high  in  lime  as  to  necessitate  the  use  of  slate  or  clay  with  it. 


34  PORTLAND  CEMENT 

Any  combination  of  materials  from  these  two  groups  may  be 
used  which  will  give  a  mixture  of  the  proper  composition  for 
burning  (See  Chapter  IV),  but  so  far  the  ones  used  in  this  coun- 
try are: — 

/.  Cement-Rock  and  Limestone. — Used  in  the  famous  Lehigh 
Valley  cement  district  in  which  more  than  half  of  the  cement 
manufactured  in  this  country  is  produced.  This  district  com- 
prises Berks,  Lehigh  and  Northampton  Counties  in  Pennsylvania, 
and  Warren  County,  New  Jersey.  In  1903,  55.2  per  cent,  of  the 
total  output  of  the  country  was  manufactured  from  this  combina- 
tion. 

2.  Marl  and  Clay  or  Shale. — Used  principally  in  Michigan, 
Ohio,  Indiana  and  Central  New  York. 

j.  Limestone  and  Shale  or  Clay. — Used  in  many  parts  of  the 
country  as  these  materials  are  widely  distributed. 

4.  Blast  Furnace  Slag  and  Limestone. — Plants  are  now  located 
for  the  manufacture  of  cement  from  these  materials  in  Illinois, 
Ohio,,  and  Pennsylvania.     These  plants  together  had  a  rated  ca- 
pacity of  about  700,000  barrels  per  year  in  1904. 

5.  Caustic  Soda  Waste  and  Clay,  formerly  used  by  one  large 
alkali  plant  in  Michigan. 

Limestone. 

- 

Limestone  is  abundantly  distributed  throughout  the  country 
and  occurs  in  many  geological  periods.  It  consists  essentially  of 
carbonate  of  lime  (or  calcium  carbonate,  CaCO3,)  and  when  pure 
forms  the  mineral  calcite.  The  principal  foreign  elements  found 
in  limestone  are  silica,  iron  oxide,  alumina,  carbonate  of  magne- 
sia and  the  alkalies,  potash  and  soda.  Limestone  sometimes  con- 
tains considerable  carbonate  of  magnesia  and  when  this  reaches 
45  per  cent,  of  the  total  carbonates,  it  is  known  as  dolomite.  To 
be  suitable  for  cement  manufacture  limestone  should  contain  but 
little  carbonate  of  magnesia — 5  per  cent,  being  about  the  limit. 
It  should  also  be  free  from  quartz  either  in  the  form  of  sand  or 
flint  pebbles.  Occasional  veins  of  flint  running  through  the  lime- 
stone bed  will  not  hurt,  since  this  may  be  sorted  out  in  quarrying. 

Since  the  limestone  must  be  reduced  to  a  fine  powder  in  order 
to  intimately  mix  with  the  clay  or  shale  used  with  it,  its  hardness 


RAW  MATERIALS  35 

is  an  important  factor  in  determining  its  suitability  for  cement 
making.  As  an  usual  thing  pure  limestone  is  very  much  harder 
than  the  impure  clayey  ones,  consequently  the  less  pure  limestones 
are  really  much  better  for  cement  manufacture  than  the  hard, 
pure  ones.  The  greatest  factor  in  the  making  of  a  sound  cement 
is  the  fine  grinding  of  the  raw  materials.  Indeed  most  plants 
using  limestone  and  clay  have  found  the  grinding -of  the  mixture 
to  the  degree  of  fineness  necessary  to  give  the  cement  a  good  hot 
test,  when  fresh,  a  very  difficult  proposition.  Some  of  them  have 
found  it  preferable  on  the  score  of  economy  not  to  make  their 
fresh  cement  pass  the  soundness  test,  but  to  let  it  season  sound 
in  their  bins. 

Such  cement  provided  it  has  seasoned  sound  is  as  good  as  any 
and  there  should  be  no  prejudice  against  its  use. 

In  South  Dakota  and  in  Alabama  there  are  found  certain  rotten 
limestones  or  chalks,  more  or  less  impure  in  composition  and 
easily  ground.  The  former  deposit  has  been  used  for  some  time 
and  the  latter  has  been  lately  utilized  for  Portland  cement  manu- 
facture. The  ease  with  which  these  chalks  or  rotten  limestones 
can  be  ground  is  a  decided  point  to  their  advantage,  and  makes 
them  most  valuable  raw  materials. 

On  the  following  page  is  a  table  giving  the  analyses  of  some 
limestones  used  for  Portland  cement  manufacture: 

Cement  Rock. 

The  impure  clayey  limestone,  used  for  the  manufacture  of  Port- 
land cement  in  the  Lehigh  District,  is  known  technically  as 
"cement  rock."  This  rock  forms  a  narrow  belt  extending  in  a 
northeasterly  direction  from  Reading,  Pa.,  to  a  few  miles  north  of 
Stewartsville,  N.  J.  It  passes  through  the  counties  of  Berks,  Le- 
high and  Northampton,  in  Pennsylvania,  and  Warren  County, 
New  Jersey,  and  is  about  fifty  miles  long  and  not  over  four  miles 
at  its  greatest  width.  There  were  in  January,  1905,  located  in 
this  district  eighteen  Portland  cement  companies  in  active  opera- 
tion, one  other  mill  completed  and  nearly  ready  to  begin  opera- 
tion and  two  in  process  of  construction.  The  mills  of  this  district 
produced  in  1903  over  55  per  cent,  of  the  output  of  the  country. 


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RAW  MATERIALS  37 

It  has  been  found  by  experience  that  a  mixture  containing 
about  75  per  cent,  carbonate  of  lime  and  18-20  per  cent,  of  clayey 
matter  (silica,  iron  oxide  and  alumina)  gives  the  best  Portland 
cement,  and  the  impure  limestones  found  in  the  Lehigh  Valley 
approach  more  or  less  nearly  this  composition.  When  this  ce- 
ment rock  contains  less  than  75  per  cent,  carbonate  of  lime  it  is 
the  practice  here  to  add  sufficient  purer  limestone  to  make  the 
mixture  of  this  proportion.  At  several  mills  around  Nazareth  the 
rock  contains  more  than  75  per  cent,  carbonate  of  lime  and  here 
instead  of  adding  limestone  it  is  necessary  to  add  a  little  slate  or 
clay  to  lower  the  percentage  of  lime. 

Geologically  this  cement  rock  is  Trenton  limestone  of  the  low- 
er Silurian  age,  and  lies  between  the  Hudson  shales  and  the  Kit- 
tatinny  magnesian  limestone.  The  upper  beds  of  the  cement  rock, 
where  it  comes  in  contact  with  the  slate  are  more  or  less  shaley 
in  composition  and  slatey  in  appearance  and  fracture.  Often  here 
the  rock  contains  less  than  50  per  cent,  carbonate  of  lime  and  is 
not  suited  to  the  manufacture  of  Portland  cement.  As  we  go 
lower  in  the  formation  the  lime  increases  until  near  the  base  of 
the  formation,  in  contact  with  the  Kittatinny  limestone  it  may 
carry  as  high  as  95  per  cent,  carbonate  of  lime.  It  is  from  these 
lower  beds  that  the  limestone  necessary  for  mixing  with  the  ce- 
ment rock  is  obtained.  The  Kittatinny  limestone  itself  is  too  high 
in  magnesia  (15  to  20  per  cent.  MgO)  to  use  for  cement  making, 
but  there  are  a  few  beds  in  this  formation  low  enough  in  magne- 
sia to  use  successfully.  The  cement  rock  itself  often  carries  5  to 
6  per  cent,  magnesium  carbonate  but  is  never  so  high  in  this  ele- 
ment as  the  Kittatinny  limestone.  The  purest  limestone  in  use  in 
the  district  contains  about  98  per  cent,  carbonate  of  lime  and 
comes  from  Annville,  Pa.,  some  50-70  miles  away. 

Cement  rock  is  considerably  softer  than  the  pure  limestones, 
usually  used  with  clay,  consequently  it  is  much  more  easily 
ground.  The  nearer  it  approaches  the  correct  composition  for 
cement  mixture  the  more  valuable  it  is.  In  general,  it  may  be 
said  that  rock  requiring  a  small  admixture  of  clay  will  prove  more 
economical  than  one  requiring  addition  of  limestone  for  a  proper 
mixture ;  since,  in  nearly  every  instance,  the  cement  rock  is  over- 
laid by  clay  which  has  to  be  removed  anyhow,  while  the  lime- 


38  PORTLAND  CEMENT 

stone  may  have  to  be  bought  or  at  least  quarried.    Equally  desir- 
able is  the  combination  of  a  high  and  a  low  lime  cement  rock. 

The  quantity  of  limestone  added  at  some  of  the  cement  mills  in 
the  Lehigh  District  is  as  much  as  50  per  cent,  of  the  rock  itself, 
and  it  is  no  uncommon  thing  when  limestone  is  bought  to  have 
this  item  alone  cost  from  5  to  10  cents  per  barrel  of  cement  pro- 
duced. A  ton  of  cement  rock  and  limestone  mixture  ready  for 
the  kilns  will  produce  from  3.1  to  3.3  barrels  of  cement.  The  ap- 
proximate quantity  of  limestone  necessary  to  use  with  any  cement 
rock  whose  analysis  is  known  may  be  found  as  follows : — 

If  the  lime  is  reported  as  carbonate,  CaCO3,  Quantity  Lime- 
stone Necessary 

_  75  — •(  %  CaCO3  in  Cement  Rock) 
~(%  CaCO3  in  Limestone)—  75   ' 

If  the  lime  is  reported  as  lime,  CaO,  Quantity  Limestone  Nec- 
essary 

_42  —  (%  CaO  in  Cement  Rock) 
( %  CaO  in  Limestone)  —  42 

The  result  in  either  event  will  be  the  number  of  pounds  of  lime- 
stone it  is  necessary  to  add  to  100  pounds  of  cement  rock,  to  make 
a  mixture  of  approximately  correct  composition  for  burning. 

Below  will  be  found  a  table  giving  the  analysis  of  some  cement 
rocks  of  the  Lehigh  District  and  also  a  very  complete  analysis 
made  by  the  author  of  a  sample  of  rock  of  practically  exact  com- 
position for  burning,  used  by  the  Dexter  Portland  Cement  Co., 
Nazareth,  Pa.  This  is  followed  by  an  equally  complete  analysis 
of  a  mixture  of  Annville  Limestone  and  cement  rock,  used  by  the 
Vulcanite  Portland  Cement  Co.,  Vulcanite,  N.  J.,  made  by  W.  F. 
Hillebrand,  of  the  U.  S.  Geological  Survey.  This  mixture  is  over 
clayed,  however,  and  undoubtedly  is  merely  a  chance  sample  and 
not  representative  of  that  company's  usual  practice. 

As  will  be  seen  by  a  reference  to  table  X,  there  is  a  considerable 
difference  in  the  analysis  of  the  various  samples.  Not  only  is  this 
true  between  samples  from  different  quarries  of  the  district  but 
also  between  samples  from  the  same  quarry.  This  is  shown  by 
table  XII,  each  sample  of  which  represents  an  average  of  n 
drill  holes  of  16  feet  each. 


RAW  MATERIALS 


39 


TABLE  X  —ANALYSES  OF  CEMENT  ROCK  USED  FOR  MANUFAC- 
TURE OF  PORTLAND  CEMENT. 


locality. 

Silica,  Si02, 

Iron  Oxide, 
Fe2O3 

Alumina, 
A1203 

Carbonate 
of  lyime, 
CaCO3 

Corbonate 
of  Magnesia 
MgC03 

18.15 
II.  10 

18.94 
17.32 
14.71 
15.05 

16.16 
19.06 

I.6l 
1.24 
1.56 
2.04 
2.10 
1.27 

1-25 
I.I4 

7.21 
4.42 
5.42 
7-07 

6.61 
9.02 

6.98 

4.44 

68.14 
77.60 

68.53 
68.91 

6954 
70.10 
70.38 
69.24 

3-88 

4.17 
3.91 
4.28 

5-ii 
3.96 
3-90 
4.21 

XToyjiretVi     Pa 

Stockertown   Pa  

Siefffried   Pa.  

Oonlav    Pa 

Alpha  N  J  

Stewartsville,  N.  J... 
Northampton,  Pa  

TABLE  XI.— COMPLETE  ANALYSES  OF  CEMENT  ROCK  AND 
CEMENT  ROCK-LIMESTONE  MIXTURE. 


Cement  Rock. 


SiO2 

13.44 

Ti02 

0.23 

A1203 

4-55 

Fe203 

0.56 

Feo 

0.88 

FeS2 

.... 

MnO 

0.06 

CaO 

41.84 

MgO 

1.94 

Na20 

0.31 

K20 

0.72 

P2O5 

0.22 

s 

0-33 

c 

0-75 

C02 

32.94 

H20  +  105 

1-55 

H20  —  105 

Dried  Sample 

100.32 


Mixture. 
I5.I8 
0.23 

4-94 
o-95 
0.46 
0.38 
0.05 
40.31 
1.65 
0.15 
0.97 

0.21 

0-54 
32.38 

I-*! 

0.38 

100.09 


PORTLAND  CEMENT 


TABLE  XII.— SHOWING  THE  VARIATIONS  IN  THE  COMPOSITION 
OF  CEMENT-ROCK  FROM  SAME  QUARRY. 


Bench. 

Analyses. 

Section  of 
Bench. 

SiO2. 

FegOg+AloOg 

CaO. 

MgO. 

"Piref    rfi  ff»f»t 

W>«;t    A 

16.26 
14.56 
16.38 
17.34 
18.94 
15-54 
17.02 
21.36 
21.98 
27.00 
16.86 
24.16 

21.15 
25.16 

7.22 

8.64 
7.90 

7-94 
6.98 
7.10 
7-30 
9.00 
8.80 
8.10 
8.14 
9.14 

9-51 
8.28 

7°-37 
72.33 
69-59 
67.93 
68.53 
71.04 

69.34 
65.41 
62.65 
69.12 

68.54 
60.69 

59-  °9 
60.42 

3-95 
3-53 
3-77 
4.19 
3.91 
4.12 
4.16 
3.96 
4.87 

4-73 
5-°7 
4-32 
4.64 
4.27 

West  B  

Center  C  •  •  •  •  • 

Second  16  feet... 

t  (                (  S          <  « 

(  (           (  (       « 
(  (           ((       (  ( 
«           «        (( 

Third  16  feet.... 
««      <  <     «  < 

«      «     <  < 
«      «  «     n 
c  i      «     (( 

Fourth  5  feet  

"West  A 

West  B  
Center  C  

East  D  

"Poof  ft 

West  A  

\\fest  jj  

Center  C  

East  E  

Center  C  

Marl. 

Cement  is  now  made  from  marl  in  Michigan,  Ohio,  New  York, 
and  Northern  Indiana.  Practically  all  the  cement  made  in  Michi- 
gan is  made  from  marl  and  clay  or  clay-shale,  the  only  exceptions, 
at  this  writing,  being  the  Alpena  Portland  Cement  Co.,  which 
uses  limestone  and  shale  found  in  the  immediate  neighborhood  of 
the  plant,  and  the  Wyandotte  Portland  Cement  Co.,  which  manu- 
factures cement  from  clay  and  limestone,  which  are  shipped  to 
the  works  from  accessible  points  on  the  lakes.  In  the  southern 
peninsular  are  located  the  plants  of  the  Bronson  Portland  Cement 
Co.,  at  Bronson;  of  the  Peerless,  at  Union  City;  of  the  Wolver- 
ine, at  Coldwater  and  at  Quincy;  of  the  Omega,  at  Mosherville; 
and  of  the  Peninsular,  at  Cement  City,  near  Jackson.  These  mills 
are  all  located  around  Coldwater  and  Jackson,  Mich.  Fifty  miles 


RAW  MATERIALS  41 

further  to  the  northeast,  are  the  mills  of  the  Egyptian  Portland 
Cement  Co.,  and  of  the  Aetna,  at  Fenton.  Still  farther  north  on 
the  shores  of  Saginaw  Bay  is  located  the  Hecla  Cement  Co.'s 
plant.  In  the  west  of  Michigan,  on  the  Muskegon  River,  the 
water  power,  of  which  it  uses  for  grinding,  etc.,  is  located  the 
Newaygo  Portland  Cement  Co.,  at  Newaygo,  and  north  of  this, 
at  Marlboro,  is  found  the  Great  Northern  Portland  Cement  Co. 
Further  north  in  the  lower  penisular,  the  one  on  one  side  and  the 
other  on  the  other  side  of  the  State,  are  the  plants  of  the  Elk 
Portland  Cement  Co.,  at  Elk  Rapids,  and  of  the  Alpena,  at  Al- 
pena.  From  this  general  outline  of  the  location  of  the  various 
plants  in  Michigan,  in  January,  1905,  it  will  be  seen  that  there  is 
no  cement  belt  here,  the  materials  for  making  cement  being  wide- 
ly scattered  throughout  the  State  and  there  being  an  abundance 
of  clay  and  marl  in  many  sections. 

In  Indiana  Portland  cement  is  manufactured  from  marl  at 
Stroh,  La  Grange  County,  by  the  Wabash  Portland  Cement  Co., 
and  at  Syracuse,  Kosciusco  County,  by  the  Sandusky  Portland 
Cement  Co.  Both  of  the  mills  are  in  the  northern  part  of  the 
State  and  are  only  a  few  miles  apart.  In  Ohio  marl  and  clay  are 
used  at  Harper,  Logan  County,  by  the  Buckeye  Portland  Cement 
Co. ;  at  Castalia,  by  the  Castalia  Portland  Cement  Co. ;  and  at 
Sandusky,  by  the  Sandusky  Portland  Cement  Co.  All  of  these 
plants  are  located  in  the  northern  part  of  the  State  near  the  lake. 
In  New  York  marl  is  used  by  the  Empire  Portland  Cement  Co., 
at  Warners ;  the  Thomas  Millen  Co.,  at  Wayland ;  the  Wayland 
Portland  Cement  Co.,  at  Wayland;  the  American  Cement  Co., 
at  Jordan;  and  the  Iroquois  Portland  Cement  Co.,  at  Caledonia. 
The  latter  plant  has  a  dry  marl  and  consequently  uses  the  dry 
process. 

Marl  is  more  or  less  pure  carbonate  of  lime,  the  principal  im- 
purities being  clay,  organic  matter  and  carbonate  of  magnesia. 
Marl  beds  usually  occupy  the  bodies  of  ancient  extinct  lakes  or 
else  the  bottoms  and  banks  of  present  ones  and  are  formed  by  the 
precipitation  of  calcium  carbonate  from  the  water  by  the  agency 
of  certain  algae  or  water  plants.  In  many  instances  the  process 
of  making  marl  beds  is  still  going  on.  Marl  is  soft  and  pulveru- 
lent, sometimes  containing  many  small  shells,  but  usually  the 


42  PORTLAND  CEMENT 

larger  part  of  it  passing  a  2OO-mesh  cement  testing  sieve.  It 
therefore  requires  little  grinding  before  burning.  White  marls 
usually  are  free  from  organic  matter,  but  the  grey  marls  often 
contain  from  5  to  10  per  cent,  of  impurities.  Marl  beds  vary  in 
size  from  a  few  acres  up  to  two  or  three  hundred.  Some  of  the 
companies  in  Michigan  each  have  marl  beds  aggregating  over 
1000  acres  and  measuring  an  average  of  20  feet  deep.  Prof. 
Campbell  has  found  that  a  cubic  foot  of  marl  contains  47.5 
pounds  of  marl  and  generally  about  48  pounds  of  water.  As  ex- 
cavated and  sent  to  the  mill,  however,  it  frequently  contains  much 
more  water  than  the  above  figure. 

Marls  for  use  in  Portland  cement  manufacture  should  be  free 
from  sand  and  pebbles.  It  is,  of  course,  possible  to  separate  the 
former  from  it  by  wash  mills  and  the  latter  by  specially  designed 
screens.  Either  operation  adds  to  the  cost  of  manufacture,  how- 
ever. Some  marls  contain  a  considerable  percentage  of  sulphur. 
From  experiments  made  by  the  author,  he  is  inclined  to  think  that 
most  of  this  sulphur  is  lost  in  the  kiln.  If  present  in  the  form  of 
iron  pyrites  or  in  combination  with  organic  matter,  it  is  simply 
burned  away.  If  present  as  calcium  sulphate  it  is  liberated  by  the 
combination  of  the  lime  with  the  silica.  Exactly  how  much  sul- 
phur is  allowable  the  author  is  not  prepared  to  say,  but  it  seems 
probable  that  at  least  5  or  6  per  cent.  SO3  might  be  present  with- 
out rendering  the  marl  unfit  for  the  manufacture  of  Portland 
cement.  Johnson1  succeeded  in  making  a  sound  true  Portland 
cement,  containing  only  1.83  per  cent,  sulphur,  in  a  small  experi- 
mental kiln  from  a  mixture  of  clay  and  gypsum.  The  raw  mate- 
rial used  by  the  Colorado  Portland  Cement  Co.,  at  Portland,  Col., 
contains  considerable  gypsum,  often  as  high  as  7  or  8  per  cent., 
yet  the  resulting  cement  contains  only  a  normal  amount  of  sul- 
phate. 

Some  marls  are  sticky  and  pasty  in  texture  and  ball  together  as 
clay  does.  Such  marls  are  hard  to  move  from  one  part  of  the 
mill  to  another  and  require  the  addition  of  more  water,  which  has 
subsequently  to  be  evaporated  in  the  kilns,  in  order  to  pump  them 
about. 

The  value   of  a   marl   bed    will    usually  lie  in  its    depth    and 

t  Cement  and  Engineering  News,  January,  1905,  p.  n. 


RAW  MATERIALS 


43 


area  and  physical  characteristics  rather  than  its  chemical  com- 
position. Marl  must,  of  course,  contain  at  least  75  per  cent,  of 
carbonate  of  lime  after  drying  and  deducting  the  organic  matter 
and  it  should  not  contain  over  2  or  3  per  cent,  free  silica  (silica 
as  quartz  sand)  nor  more  than  5  per  cent,  carbonate  of  magnesia. 
The  greater  the  depth  of  the  bed  the  more  economically  it  can  be 
worked.  If  the  beds  are  dry  so  that  the  dry  process  of  manu- 
facture can  be  employed  the  value  of  the  deposit  is  greatly  in- 
creased thereby. 

Usually   marls   require  the   addition  of  about  one-fifth  their 
weight  (when  dry)  of  dry  clay  for  burning.     The  approximate 
proportion  in  a  specific  case  may  be  found  as  follows : 
Weight  of  Clay  = 

(%  CaO  in  Marl)— 42 
42  — (%  CaO  in  Clay) 

The  result  gives  the  weight  of  clay  (in  pounds)  to  be  added 
to  100  Ibs.  of  marl.  If  in  the  analysis  lime  is  reported  as  carbon- 
ate of  lime,  multiply  this  percentage  by  0.56  for  the  equivalent 
percentage  of  lime,  CaO. 

Table  XIII  gives  the  analysis  of  some  marls  used  for  Portland 
cement  making : 

TABLE  XIII.— ANALYSES  OF  MARLS  USED  FOR  MAKING 
PORTLAND  CEMENT. 


X  100 


Used  by 

6' 
3 

| 

i 

Alumina,  AlaOs. 

V 

13 

s4 
r 

Carbonate  of 
lyime,  CaCo3. 

Carbonate  of 
Magnesia,  MgCO3. 

Sulphur  Trioxide, 
S03. 

Organic  Matter. 

Bronson    Portland   Cement 

T   7^ 

j 

c7 

87  Q2 

Wolverine  Portland    Cement 
Co.,  Cold  water,  Mich  
Omega  Portland  Cement  Co., 

*»7v 

0.52 
O  QI 

0.5I 

o/ 

0-53 

2O 

o/.yz 
92.25 
QI   I  2 

2.87 
2  g8 

u.i^ 
0.89 

•5° 

Peninsular  Portlant    Cement 
Co.,  Woodstock,  Mich  
Detroit  Portland  Cement  Co., 

0.38 

o  48 

0. 

O  17 

*3> 

68 

OCT 

V«3>li£ 
90.66 

Ql     0^ 

1.81 
•*  88 

"•  o1 
trace 

O    ^<N 

2.  13 

Empire  Portland  Cement  Co., 
Warners   N   Y  

O  ^O 

v.  i/ 
O  2O 

O  IO 

Vo-^o 

96  16 

i  20 

U>00 

o  80 

I  04. 

44  PORTLAND  CEMENT 

Clay. 

Clay  consists  of  a  mixture  of  kaolin  with  more  or  less  sand  and 
other  impurities.  Kaolin,  sometimes  called  kaolinite,  is  a  hy- 
drated  silicate  of  alumina,  having  the  symbol  Al2O32SiO22H2Q. 
Sand  is  composed  of  grains  of  quartz  and  other  minerals.  Clay 
contains  silica  both  as  chemically  combined  silica  in  kaolin  and 
the  other  minerals,  and  in  the  free  state  as  quartz  sand.  Clay  also 
contains  more  or  less  iron  oxide,  lime  and  magnesia  and  smaller 
quantities  of  potash  and  soda.  Clay  originates  from  the  disinte- 
gration of  rocks  containing  minerals  made  up  largely  of  alumina 
and  silica.  The  most  abundantly  occurring  of  these  minerals  are 
the  feldspars,  augite  and  hornblende.  Nephelite  and  sodalite  oc- 
cur also  to  a  much  smaller  extent.  Decomposition  takes  place  by 
the  gradual  leaching  out  of  the  more  soluble  elements  of  the  min- 
erals by  water,  leaving  behind  the  less  soluble  ones,  silica  and 
alumina,  together  with  smaller  proportions  of  lime,  magnesia, 
iron,  potash  and  soda.  These  insoluble  portions  are  washed  over 
and  over  again  and  deposited  in  favorable  places  by  water.  Such 
deposits  are  called  sedimentary  clay,  while  clay  which,  instead  of 
being  washed  away  by  water,  is  left  near  the  rocks  from  whose 
decomposition  it  was  formed  is  called  residual  clay.  The  potter 
deals  more  particularly  with  the  plasticity,  permanence  when 
burnt  and  refractoriness  of  clay,  but  to  the  Portland  cement 
manufacture  these  properties  are  of  very  secondary  importance. 
The  main  thing,  of  course,  is  the  chemical  composition  and  the 
state  of  subdivision  in  which  the  silica  exists.  Roughly  speaking, 
the  clay  should  contain  at  least  2.3  times  as  much  silica  as 
alumina.  Iron  may  replace  alumina  to  almost  any  extent  without 
detriment  to  the  cement  made  therefrom.  Magnesia  and  lime 
are  usually  present  only  in  small  quantities,  the  more  of  the  latter 
present  the  better,  but  the  former  should  be  low,  (not  over  3  or  4 
per  cent.).  The  alkalies  should  not  run  over  3  per  cent.,  as  an 
excess  is  likely  to  cause  unsound  and  quick  setting  cement. 

Most  clays  will  meet  with  the  above  requirements,  the  usual 
point  to  be  looked  into  most  carefully  is  the  condition  of  the  sil- 
ica. All  clay  contains  some  uncombined  silica,  present  as  quartz 
sand  or  pebbles.  The  latter  may  be  separated  from  the  clay  by 
mechanical  means  so  the  former  is  the  one  which  gives  most. 


RAW  MATERIALS 


45 


trouble.  The  sand  must  be  present  in  the  clay  in  a  very  finely 
divided  condition.  If  much  (over  5%)  is  present  in  the  form  of 
grains  not  passing  a  loo-mesh  sieve,  the  clay  is  unsuited  to  ce- 
ment manufacture.  Under  the  section  on  "Analysis  of  the  Raw 
Materials"  a  method  is  given  for  determining  the  quartz  sand  fail- 
ing to  pass  a  loo-mesh  test  sieve. 

Below  are  some  analyses  of  clays  used  in  making  cement : 

TABLE  XIV.— ANALYSES  OF  CLAYS  USED  FOR  THE  MANU- 
FACTURE OF  PORTLAND  CEMENT. 


o* 

a" 

d 

bo 

,c 

§ 

2 

^S1 

44 

2  _ 

d 

a) 

So* 

•g 

5 

cc 

***  Q5 

0 

rt" 

.a® 

bo 

s 

Used  by 

$ 

I 

g 

II 

V 

•g 

§ 

1 

83 

j3 

fl 

O 

3 

bo 
rt 

^ 

1 

2 

" 

cc 

M 

Alpena  Portland  Cem. 
Co.,  Alpena,  Mich  .. 

61.09 

19.19 

6.78 

2.51 

0.65 

1.42 

5.13 

Limestone 

Bronson  Portland  Cem. 

Co.  Bronson,  Mich.. 

63.75 

16.40 

6.35 

2.40 

1.42 

0.14 

6.89 

Marl 

Buckeye  Portland  Cem. 

Co     Harper  O  

CO    f"l 

17  O 

50 

20.  o 

I.O 

32 

Marl 

Catskill    Cement     Co., 

i  /.«j 

•*-* 

•^ 

Smiths  Landing,  N.  Y. 

61.92 

16.58 

7.28 

2.01 

1.58 

trace 

.... 

Limestone 

Glenn's  Falls  Port.  Cem 

Co.,  Glenn's  Falls,N.Y 

55.27 

28 

15 

5.84 

2.25 

0.12 

.... 

Limestone 

Newago  Portland  Cem. 

Co.,  Newago,  Mich.. 

55.84 

8.90 

3-02 

9.98 

5-16 

.... 

13.68 

Marl 

Pacific   Portland   Cem. 

Co.,  Suisun,  Cal  

58.44 

18.95 

7-55 

1.70 

1.88 



9.07 

Limestone 

Shale. 

For  practical  cement  making  purposes  shale  may  be  looked 
upon  as  merely  solidified  clay,  since  the  chemical  composition  of 
the  two  are  very  similar  and  the  same  regard  must  be  had  as  to 
the  state  of  subdivision  of  the  free  silica.  Shale  is  preferable  to 
clay  for  mixing  with  limestone  since  segregation  of  the  two  is  less 
likely  to  take  place.  It  also  carries  less  water  and  consequently 
does  not  require  so  much  drying  before  grinding.  Clays  on  the 
other  hand  are  better  suited  to  mixing  with  marls  because  of  the 
similarity  in  physical  properties  between  the  two.  ^If  a  mixture  of 
dry  clay  and  coarsely  ground  limestone  is  poured  from  a  spout 
into  a  pile  the  clay  will  remain  in  the  center  of  the  pile  and  the 


46 


PORTLAND  CEMENT 


limestone  will  roll  down  the  sides  of  the  pile.  Now,  if  this  pile  is 
tapped  from  below  in  the  middle,  as  it  would  be  in  a  bin,  the  first 
material  drawn  would  be  most  of  it  clay,  while  the  last  of  it  would 
be  practically  all  limestone.  To  overcome  this  tendency  to  segre- 
gate, therefore,  it  is  best  to  mix  substances  of  like  physical  char- 
acteristics, shale  with  limestone  and  clay  with  marl. 

Table  XV  gives  some  analyses  of  shales  used  in  the  manufac- 
ture of  Portland  cement : 

TABLE  XV.— ANALYSES  OF  SHALES  USED  FOR  THE  MANU- 
FACTURE OF  PORTLAND  CEMENT. 


i 

1 

I    • 

O 
rt 

O 
be 

1** 

1 

j 

Used  by 

-• 

.9 

O      C< 

O 
oT 

rf 
Ti 

CJ 

C3 

1 

2 

1 

sfa 

p 

<u 
o 

^'C 

O 

^ 

3 

p 

'S 

3 

bo 

C^'O 

V) 

^ 

3 

o 

i 

CO 

3. 

Hudson  Portland  Cem. 

Co.,  Hudson,  N.  Y.. 
Southern   States    Port- 

62.39 

20.26 

7.3i 

0-33 

1.49 

— 

8.03 

Limestone 

land     Cement     Co., 

Rockmart   Ga  

C7  -ic 

21.  l8 

377 

.      Q 

2  OO 

Coldwater  shales  in  use 

0/-OJ 

•  // 

7- 

by  several  Michigan 

mills  «  •  •       •        • 

62  10 

2O  OQ 

7  81 

O6^ 

O^A 

. 

^7    r\r\ 

/.Ol 

.  wO 

0.49 

7.90 

Blast  Furnace  Slag. 

In  1897  the  Clinton  Cement  Co.  in  connection  writh  the  Clinton 
Iron  and  Steel  Co.,  erected  a  small  plant  for  the  manufacture  of 
Portland  cement  from  limestone  and  slag,  at  Pittsburg,  and  in 
1900,  the  Illinois  Steel  Co.  began  the  manufacture  of  Portland 
cement  from  blast  furnace  slag  and  limestone  at  their  South  Chi- 
cago works.  This  plant  has  a  capacity  of  1500  barrels  a  day. 
The  company  has  also  under  construction  at  this  writing  a  larger 
plant,  known  as  its  Burfington  plant,  at  Indiana  Harbor,  Ind., 
south  of  Chicago,  and  one  at  the  Carnegie  Steel  Works,  at  Pitts- 
burg.  The  Buffington  plant  which  is  nearing  completion  will 
have  a  capacity  of  about  4000  barrels  a  day. 

There  are  two  kinds  of  cement  made  from  blast  furnace  slag 
and  the  two  must  not  be  confused,  one  a  true  Portland  made  by 
mixing  limestone  and  slag,  grinding  very  finely  the  resulting  mix- 


RAW  MATERIALS  47 

ture  and  then  burning  just  as  if  the  raw  materials  were  clay  and 
limestone  or  cement-rock  and  limestone;  the  other  a  puzzolan  or 
slag  cement  made  by  grinding  with  slaked  lime  suitable  slag, 
which  has  been  previously  chilled  suddenly  by  dropping  into 
water.  The  resulting  mixture  is  then  ready  for  use  and  is  not 
burned. 

^"  At  the  Illinois  Steel  Company's  South  Chicago  plant  the  slag 
is  granulated  by  cooling  it  suddenly  with  water,  dried,  ground, 
and  then  mixed  with  the  proper  proportion  of  ground  limestone. 

Slag  suitable  for  the  manufacture  of  Portland  cement  can  only 
come  from  furnaces  working  on  pure  ores,  such  as  those  of  the 
Lake  Superior  mines,  and  fluxed  with  low  magnesian  limestone. 
Generally  speaking,  the  slag  must  analyze  within  the  following 
limits : 

Silica,  plus  Alumina,  not  over  48  per  cent. 

Iron  and  Alumina,  12  to  14  per  cent. 

Magnesia,  under  3  per  cent. 

There  is  a  slight  thermal  advantage  in  using  slag  for  the  manu- 
facture of  Portland  cement.  The  lime  is  present  as  oxide,  just  as 
it  is  in  cement,  and  no  heat  is  required  to  decompose,  as  is  the 
case  with  limestone  where  heat  is  required  to  change  the  carbon- 
ate to  oxide. 

This  advantage,  however,  is  negatived  to  some  extent  by  the 
necessity  of  driving  off  the  water  used  to  granulate  the  slag.  Even 
were  this  latter  not  the  case,  under  the  present  wasteful  system  of 
burning  cement,  this  saving  would  hardly  be  appreciable. 

Below  is  an  analysis  of  a  typical  slag  used  by  the  Illinois  Steel 
Co.  in  making  their  "Universal"  Portland  cement. 

Silica 33.10 

Iron  Oxide  and  Alumina 12.60 

Lime .s 49.98 

Magnesia  ...   2.45 

Alkali  Waste. 

The  precipitated  calcium  carbonate  obtained  from  the  manu- 
facture of  caustic  soda  by  the  Leblanc  process  has  been  used  suc- 
cessfully in  Europe  for  the  manufacture  of  Portland  cement.  The 
Michigan  Alkali  Co.,  Wyandotte,  Mich.,  however,  in  1899,  built 


48  PORTLAND  CEMENT 

a  small  plant  designed  to  take  care  of  100  tons  of  waste.  This 
plant  has  now  been  leased  to  the  Wyandotte  Portland  Cement  Co., 
which  uses  limestone  in  place  of  the  alkali  waste  so  that  the  pre- 
sumption is  that  the  process  did  not  pay.  It  seems  hardly  likely 
that  alkali  waste  will  be  used  again  in  this  country  in  view  of  the 
availability  of  much  more  suitable  materials.  Those  who  are  in- 
terested in  the  process,  however,  will  find  a  paper  of  some  length 
on  the  subject  in  "Cement  and  Engineering  News"  of  March  and 
April,  1900. 

Below  is  an  analysis  of  the  alkali  waste  used  by  the  Michigan 
Alkali  Co. : 

Per  cent. 

Silica 0.60 

Alumina  and  Iron  Oxide 3.04 

Carbonate  of  Lime 95.24 

Carbonate  of  Magnesia i.oo 

Alkalies 0.20 

Gypsum. 

Gypsum  either  in  its  native  state  or  after  calcining  is  always 
added  to  Portland  cement  to  regulate  the  set  for  reasons  which 
will  be  explained  in  Chapter  XV,  and  hence  may  be  consid- 
ered as  one  of  the  raw  materials  of  its  manufacture.  It  consists 
of  hydrated  sulphate  of  lime,  CaSO4.2H2O.  This  is  usually  con- 
taminated by  the  presence  of  more  or  less  silica,  iron  and  alumina, 
carbonates  of  lime  and  magnesia,  organic  matter  and  sulphides. 
Gypsum  is  found  in  many  localities  in  this  country  and  in  Nova 
Scotia  and  New  Brunswick.  From  the  latter  places  it  is  largely 
imported  for  use  in  the  cement  trade,  for  making  wall  plaster, 
plaster  of  Paris,  etc. 

When  gypsum  is  heated  to  132°  C  it  loses  three- fourths  of  its 
water  of  crystallization  and  another  hydrate  is  formed  having 
the  formula  (CaSO4)2.H2O  and  commonly  known  as  plaster  of 
Paris  or  calcined  plaster.  If  gypsum  is  heated  to  a  temperature 
of  343°  C  all  the  water  is  driven  off  and  it  is  converted  to  anhy- 
drite which  has  the  formula  CaSO4,  and  is  known  usually  as  dead 
burned  plaster. 

Either  gypsum  or  plaster  of  Paris  may  be  used  to  slow  the  set 
of  cement.  If  the  retarder  is  to  be  added  to  the  clinker  before  the 
latter  is  ground  gypsum  is  usually  used.  If  the  addition  is  to  be 


RAW  MATERIALS 


49 


made  at  the  stock  house,  when  the  cement  is  being  packed,  finely 
ground  plaster  of  Paris  is  used.  In  valuing  gypsum  or  plaster  of 
Paris  for  cement  manufacture  the  main  requisite  is  the  quantity 
of  sulphate  of  calcium  or  SO3  it  contains,  and  the  purchaser  has 
to  take  into  consideration  chiefly  how  much  of  this  he  is  getting 
for  his  money.  In  the  case  of  plaster  of  Paris  its  fineness  should 
also  be  taken  account  of,  if  it  is  to  be  added  to  ground  cement. 
The  finer  the  plaster,  the  better  it  is  for  this  purpose. 

A  cement  mill  manufacturing  1000  barrels  a  day  will  use  about 
4  tons  of  gypsum  or  plaster  per  day.  This  is  usually  purchased 
from  some  dealer  and  arrives  at  the  mill  in  bags,  the  gypsum 
being  crushed  to  pass  an  inch  perforated  screen. 

Below  are  the  analyses  of  some  gypsums  used  in  retarding  the 
set  of  Portland  cement : 

TABLE  XVI.— SHOWING  ANALYSIS  OF  SOME  GYPSUMS  USED  IN 
THE  MANUFACTURE  OF  PORTLAND  CEMENT. 


From 

SiO2. 

AloOg  + 

FeoOo. 

CaCO3. 

MgCO3. 

CaSO4. 

H2O. 

O  IO 

o  04 

Or6 

Oil 

78   rj 

Michigan  •  

T   IT 

o  64 

2   27 

o  18 

/"•O1 
7fi  8? 

*«o* 

T    l8 

••*/ 

/U.Oj 

mO    n/l 

rn  nS 

New  York  

211 

•*5 

o  61 

i  18 

•5a 

70.  04 

19.90 

Ohio  , 

o  68 

/°'OL 

~Q  nQ 

19-3° 

The  Valuation  of  Raw  Materials. 

In  passing  on  the  availability  of  raw  material  for  cement  manu- 
facture, a  number  of  things  must  be  considered  besides  mere 
analysis.  The  cost  of  quarrying  or  excavating,  the  power  re- 
quired to  grind  and  the  coal  it  will  take  to  burn  it  must  be  con- 
sidered. With  excavating  we  include  also  cost  of  conveying  to 
the  mill.  Marl  and  clay  are  the  easiest  raw  materials  to  excavate, 
but  on  the  other  hand  the  mill  can  seldom  be  located  near  the  beds 
of  the  former,  owing  to  the  necessity  of  having  the  mill  located 
on  firm  dry  ground.  This  necessitates  pumping  or  carrying  the 
marl,  in  some  instances  several  miles  and  increases  the  cost  of 
manufacture.  A  very  shallow  marl  bed  can  not  be  worked  as 


50  PORTLAND  CEMENT 

economically  as  a  deep  one  because  of  the  constant  moving  about 
of  the  excavating  apparatus,  etc.  When  the  marl  beds  are  located 
in  the  north,  cold  weather  is  apt  to  tie  them  up  by  the  freezing 
of  the  lake  over  them,  necessitating  either  the  cutting  of  the  ice 
or  the  shutting  down  of  the  mill.  Both  add  to  the  cost  of  produc- 
tion. Cement-rock  is  usually  blasted  down,  loaded  on  cars  and 
hauled  by  cable  to  the  mill,  close  at  hand.  It  costs  more  in  pow- 
der and  drilling  than  marl,  but,  if  a  steam  shovel  is  used  to  load 
the  cars,  costs  less  after  it  is  down  to  convey  to  the  mill  than  marl, 
as  only  half  as  much  material  has  to  be  handled  owing  to  the  water 
in  the  marl.  Even  when  loaded  by  hand  the  cost  of  quarrying 
cement-rock  is  no  greater  than  that  for  marl.  A  recent  writer1 
places  the  cost  of  excavating  marl  at  21  cents  a  ton,  while  the 
writer  knows  of  several  mills  where  the  delivery  of  cement-rock 
to  the  crushers  is  done  at  a  smaller  figure  than  this.  Limestone 
is  harder  than  cement-rock  and  costs  more  to  drill,  blast  and 
break  up  the  lumps  into  sizes  suitable  for  loading  on  the  cars  or 
carts.  Shale  will  cost  about  the  same  as  cement  rock  to  quarry  and 
load,  but  the  mill  is  usually  located  near  the  limestone  deposit 
or  marl  beds,  as  much  more  of  these  are  needed,  consequently  the 
shale  must  usually  be  carried  some  distance  to  the  mill.  The 
cost  of  getting  out  either  cement-rock  or  limestone  will  be  influ- 
enced by  the  amount  of  "stripping"  that  has  to  be  done.  In  some 
mills  this  top  can  be  used,  in  which  case  this  cost  is  saved. 

Marl  and  clay  are  the  easiest  materials  to  grind,  shale,  cement- 
rock  and  chalky  limestone  come  next,  while  limestone  and  slag 
are  harder  still.  Slag  is  brittle  but  hard,  breaks  up  to  a  size  pass- 
ing a  2O-mesh  sieve  easily,  but  requires  considerable  additional 
grinding  to  make  95  per  cent,  of  it  pass  a  loo-mesh  sieve. 

Cement  rock-limestone  mixture  burns  easiest  of  any  of  the 
combinations  in  the  kilns,  limestone-clay,  and  slag-limestone  mix- 
tures are  harder  still  and  the  wet  marl  and  clay  mixture  requires 
much  more  coal  than  any  other.  In  this  case,  burning  and  drying 
are  considered  together.  Cement  rock  seldom  contains  more  than 
$%  moisture  and  limestone  even  less  as  it  comes  from  the  quarry. 
Slag  may  carry  15  or  20  per  cent,  of  water  left  in  from  the  process 
of  granulation,  and  marl  50  to  60  per  cent.  The  more  intimate 

1  Soper,  Cement  and  Engineering  News,  Feb.,  1894. 


RAW  MATERIALS  51 

mixture  of  the  argillaceous  and  calcarious  elements  of  the  ce- 
ment rock-limestone  mixture  makes  it  easier  to  burn  than  the 
equally  dry  limestone-clay  combination,  while  the  large  quantity 
of  water  to  be  driven  off  in  the  kilns  makes  the  burning  of  the 
marl-clay  combination  so  costly.  If  marl  and  clay  are  introduced 
into  the  kiln  dry  they  require  no  more  fuel  to  burn  than  the  ce- 
ment rock  limestone  combination.  The  subjects  of  burning  and 
grinding  are  treated  of  to  greater  length  in  special  chapters  and 
they  should  be  consulted  for  data  relative  to  the  cost  of  manu- 
facturing Portland  cement  from  various  kinds  of  raw  material. 

Portland  cement  can  be  made  from  such  a  variety  of  materials 
that  almost  every  geological  report  will  show  analyses  of  hun- 
dreds of  limestones,  clays,  shales  and  marls  suitable  for  the  manu- 
facture of  cement. 

The  mere  fact  therefore  that  raw  materials  of  suitable  chemical 
composition  for  the  manufacture  of  Portland  cement  exists  in  a 
certain  locality  is  no  occasion  for  the  erection  of  a  mill  on  this 
site,  because  the  success  of  the  enterprise  will  depend  more  upon 
local  conditions  than  upon  the  raw  materials  themselves.  The 
cost  of  fuel,  labor  and  supplies  must  be  taken  into  consideration 
as  well  as  the  ability  to  market  the  product.  The  fuel  item  in  the 
manufacture  of  Portland  cement  is  a  big  one,  dry  material  re- 
quiring from  165  to  200  Ibs.  of  fuel  per  barrel  of  cement  and  wet 
material  from  200  to  250  Ibs.,  under  the  usual  system,  for  burning 
and  grinding. 

Portland  cement  is  so  bulky  in  proportion  to  its  value  that  the 
nearness  of  the  mill  to  the  market  is  also  an  important  item. 

The  Lehigh  District  is  blessed  with  a  soft  easily  ground  cement 
rock,  but  it  probably  owes  its  development  also  to  cheap  coal  and 
labor,  experienced  men  and  its  proximity  to  such  markets  as  New 
York,  Philadelphia  and  Boston. 


CHAPTER  IV. 


PROPORTIONING  THE  RAW  MATERIAL 


While  a  glance  at  the  table  of  analysis  on  page  16  will  show 
wide  variation  in  the  chemical  composition  of  Portland  cement, 
it  must  not  be  supposed  that  such  latitude  in  proportioning  the 
raw  materials  really  exists.  If  the  resulting  Portland  cement  is  to 
be  sound,  normal  setting,  and  of  good  strength,  it  is  imperative 
that  the  raw  materials  shall  be  correctly  proportioned,  as  to  the 
balance  between  the  silica  and  alumina  on  the  one  hand  and  the 
lime  on  the  other.  Cements  from  different  mills  often  vary  sev- 
eral per  cent,  from  each  other  as  to  the  silica,  lime  and  alumina, 
and  yet  one  appears  as  good  as  the  other.  This  variation  is  often 
due  in  part  to  addition  of  gypsum  to,  and  the  contamination  by 
the  coal  ash  of  the  clinker  and  also  to  the  absorption  of  carbon 
dixoide  from  the  air.  It  is  still,  however,  evident  that  this  will 
not  account  for  all  the  variations,  and  that  the  raw  mixtures  from 
which  cement  is  made  vary  widely,  within  certain  limits,  at  the 
different  works.  Many  attempts  have  been  made  to  put  the  cal- 
culation of  cement  mixtures  on  a  strictly  scientific  basis.  So  far 
as  the  work  at  the  same  mill  is  concerned,  this  has  been  success- 
ful; and  it  is  comparatively  easy,  after  a  little  observation  and 
experimenting,  to  formulate  a  rule  which  will  hold  good  for  the 
mill  in  question;  but  when  it  comes  to  putting  this  into  practice 
elsewhere,  failures  may  result.  Unquestionably  as  our  knowl- 
edge of  the  constitution  of  Portland  cement  increases  and  our 
knowledge  of  the  role  played  by  the  alkalies,  iron,  etc.,  during 
clinkering  becomes  more  certain,  we  will  be  able  to  work  out 
with  mathematical  precision  the  composition  of  cement  mixtures. 

Michaelis,  Sr.,  Le  Chatelier  and  Newberry  have  all  proposed 
formulas  for  the  correct  proportioning  of  the  raw  materials. 

Dr.  Michaelis1  bases  his  formula  on,  what  he  calls,  the  "hy- 

1  Cement  and  Engineering  News,  August,  1900. 


PROPORTIONING  RAW  MATERIAL  53 

draulic  modulus,"  a  factor  representing  the  ratio  between  the  per 
centage  of  lime  and  the  combined  percentages  of  silica,  alumina 
and  iron  oxide  present  in  Portland  cement.  He  states  that  this 
ratio  must  lie  within  the  limits  of  1.8  and  2.2  and  proposes  the 
empirical  figure  2.  His  formula  stated  in  the  form  of  an  equa- 
tion is — 

%  Lime 


%  Silica  +  %  Iron  Oxide  +  %  Alumina 

The  writer  has  found  this  formula  will  in  some  instances  give 
a  mixture  which  would  result,  when  burned,  in  a  very  much 
over-clayed,  underlimed  and  consequently  quick-setting  ce- 
ment. It  does  not  seem  to  be  applicable  to  all  conditions. 
Of  four  cements  analyzed  by  the  writer  recently,  each  from  a 
different  mill,  the  ratios  were:  A.  1.92,  B.  2.01,  C.  2.07,  D.  2.18. 
Any  cement  made  at  mill  D  with  this  formula  would  have  been 
decidedly  quick-setting.  When  the  contamination  of  the  cement 
by  the  fuel  ash  is  taken  into  consideration  it  is  probable  that  A 
is  the  only  one  of  these  four  cements  in  which  the  ratio  between 
the  lime  and  the  silicates  before  burning  was  2. 

Newberry  followed  up  his  paper  on  the  constitution  of  Port- 
land cement,  mentioned  in  Chapter  II,  with  the  first  formula, 
based  on  scientific  rather  than  empirical  knowledge,  of  which  the 
writer  knows.  Considering  cement  to  be  composed  of  tricalcium 
silicate,  3CaO.SiO2,  containing  2.8  times  as  much  lime  as  silica, 
and  dicalcium  aluminate,  2CaO.Al2O3,  containing  i.i  times  as 
much  lime  as  alumina,  he  proposed  the  following : 

Lime  =  silica  X  2.8  +  alumina  X  i.i 

or 
Carbonate  of  Lime  =  silica  X  5  +  alumina  X  2. 

As  this  formula  represents  the  maximum  of  lime  which  a  cement 
could  carry,  if  it  were  manufactured  under  ideal  conditions  as  to 
grinding  and  burning,  conditions  which  are  never  met  with  in 
practice,  he  found  it  necessary  in  actual  work  to  carry  the  lime 
a  little  lower  than  that  called  for  by  the  formula,  say  between  95 


54  PORTLAND  CEMENT 

and  98  per  cent,  of  the  maximum.     Ninety-five  per  cent,  of  the 
maximum  would  give  the  following: 

Carbonate  of  Lime  =•  silica  X  4-8  +  alumina  X  i  -9- 
As  an  example  of  the  method  of  using  the  formula  let  us  sup- 
pose we  wish  to  make  a  cement  mixture  from  limestone  and  ce- 
ment rock  of  the  following  composition : 

ANALYSES. 

Cement  Rock.  limestone. 

Silica 19-06  2.14 

Iron  Oxide 1.14  -46 

Alumina 4-44  i-°° 

Carbonate  of  Lime 69.24  94.35 

Carbonate  of  Magnesia 4.21  2.18 

The  calculation  is  as  follows : 

LIMESTONE. 

Total  carbonate  of  lime 94-35 

Silica,         2.14X4-8  =  10.27 

Alumina,    i.ooXi-9  —    I-9°  I2-I7 

Available  carbonate  of  lime 82. 18 

CEMENT  ROCK. 

Silica,         i9.o6X4-8  =  9I-49 
Alumina      4.44X1.9=   8.44 

99-93 

Less  carbonate  of  lime  contained 69.24 

Required  carbonate  of  lime  for  100  parts 30-69 

The  number  of  parts  of  limestone  required  for  ioa  parts  ce- 
ment-rock will  then  be 

30.69  X  IPO 
82.18 

37.3  Ibs.  limestone  contain 35- r9  IDS-  CaCO3 

loo.o  "     cement  rock     "     69.24    "         " 


137.3"      mixture 104.43    ^ 

Mixture  should,  therefore,  analyse: 

104.43  X  IPO  =    6  Q  yo  carbonate  of  lime 

137.3 
A  table1  for  saving  the  multiplication  in  this  calculation  is 

1  Meade,  Cement  and  Engineering  News,  December,  1901. 


PROPORTIONING  RAW  MATERIAL 


55 


shown  in  Fig.  I.  It  is  made  of  cross-section  or  co-ordinate  paper, 
such  as  can  be  bought  by  the  sheet  or  yard  from  any  dealer  in 
draughtsman's  supplies.  The  paper  ruled  in  squares  every  centi- 


/oc 


80 


6O 


dK 


O 


^^ 


tic^ 


Fig.   i.     Graphic  Method  of  Proportioning  Cement  Mixture. 

meter  with  broad  lines  and  these  spaces  divided  again  into  tenths 
by  fine  lines  is  best  for  this  use.  A  sheet  of  this  of  sufficient  size 
to  cover  all  raw  material  used  in  the  particular  plant  is  either 
pasted  to  a  sheet  of  stiff  card  board  or  tacked  to  a  drawing 
board.  After  drying,  the  large  divisions  on  the  lower  margin  are 
numbered  i,  2,  3,  etc.,  to  correspond  to  the  percentages  of  silica 
and  alumina  in  the  clay,  while  the  divisions  of  the  same  size  on 
the  right  and  left  hand  margins  are  numbered  5,  10,  15,  etc.,  to 
correspond  to  pounds  of  calcium  carbonate.  Now  two  lines  are 
drawn,  one  making  an  angle  of  45°  with  the  horizontal  margin 


56  PORTLAND  CEMENT 

and  passing  through  the  O,  O  point,  the  other  passing  through 
the  same  O,  O  point  but  making  an  angle  of  21°,  48'.  The  first 
line  represents  the  "calcium  carbonate-silica"  ratio  and  should  be 
so  designated,  the  second  the  "calcium  carbonate-alumnia"  ratio. 
The  abscissas  (figures  on  the  lower  margin)  of  points  on  the  cal- 
cium carbonate-alumina  line  represent  the  percentage  of  silica  in 
the  cement-rock  and  the  ordinates  (figures  on  the  side  margins) 
the  corresponding  weight  of  calcium  carbonate.  Similarly  the  ab- 
scissas of  points  on  the  calcium  carbonate-alumina  line  express 
the  percentage  of  alumina  and  the  ordinates  of  these  points  the 
corresponding  weight  of  calcium  carbonate.  As  an  example,  to 
explain  the  use  of  the  table,  suppose  we  wish  to  know  how  much 
calcium  carbonate  to  mix  with  a  rock  of  the  composition : 

Per  cent. 

Silica 18.0 

Alumina,  etc 8.3 

Calcium  carbonate 67.3 

Other  constituents 5-9 


First  find  the  calcium  carbonate  equivalent  to  the  silica  in  the 
stone.  To  do  this  run  up  the  vertical  line  corresponding  to  18  to 
"c"  where  it  cuts  the  line  marked  "calcium  carbonate  silica."  The 
ordinate  "b"  of  this  point,  (found  by  running  along  the  nearest 
horizontal  line  to  "c"  to  the  margin)  or  90,  will  be  the  weight  of 
calcium  carbonate  equivalent  to  the  silica.  Next  find  the  calcium 
required  for  the  alumina  by  running  up  the  vertical  line  corre- 
sponding to  8.3  to  "d"  where  it  cuts  the  line  marked  "calcium 
carbonate-alumina"  and  then  along  the  nearest  horizontal  line  to 
this  point  to  the  side  margin.  The  reading  here  "e"  or  16.6  will 
be  the  weight  of  calcium  carbonate  required  for  the  alumina.  The 
silica  and  alumina  together  of  course  will  require  16.6  +  90  or 
106.6  pounds  of  calcium  carbonate,  but  since  the  cement  rock 
contains  67.3  per  cent,  calcium  carbonate  it  is  only  necessary  to 
add  to  it  106.6  —  67.3  or  39.3  pounds  of  calcium  carbonate. 

It  is  not  necessary  to  use  a  protractor  in  drawing  the  "calcium 
carbonate-alumina"  and  the  "calcium  carbonate-silica"  lines.  It 
is  evident  that  both  lines  must  pass  through  the  O,  O  point.  Any 
other  point  through  which  they  must  pass  may  be  quickly  found 


PROPORTIONING  RAW  MATERIAL  57 

by  calculation  and  the  lines  drawn  through  these  two  points.  For 
example  25  per  cent,  silica  will  require  25x5  or  125  pounds  of 
calcium  carbonate.  So  if  the  line  "calcium  carbonate-silica"  is 
drawn  through  the  O,  O  point  and  the  point  of  intersection  be- 
tween the  vertical  line  corresponding  to  25  per  cent,  silica  and  the 
horizontal  line  corresponding  to  125  pounds  of  calcium  carbonate, 
it  will  have  the  proper  angle.  Similarly  the  alumina  line  should 
be  drawn  through  the  O,  O  point  and  that  of  the  intersection  of 
the  vertical  line  corresponding  to  25%  alumina  and  the  horizontal 
line  corresponding  to  25x2  or  50  Ibs.  of  calcium  carbonate. 

The  substitution  of  any  other  lime-silica  and  alumina  ratio  than 
that  represented  by  Newberry's  formula  can  easily  be  effected. 
For  example  let  us  suppose  that  in  a  given  plant  Newberry's  for- 
mula gives  an  "overlimed"  cement,  and  that  a  formula 

Calcium  carbonate  =  %  silica  X  4.9  +  %  alumina  X  1.96 
gives  better  results.  Then  in  order  to  express, this  ratio  it  is  nec- 
essary to  draw  the  silica  line  through  the  O,  O  point  and  the 
point  of  intersection  of  the  vertical  line  representing  25%  silica 
and  the  horizontal  line  representing  25x4.9  or  122.5  pounds  cal- 
cium carbonate.  The  alumina  line  is  drawn  through  the  O,  O 
point  and  that  of  the  intersection  of  the  vertical  line  representing 
25%  alumina  and  of  the  horizontal  line  25x1.96  or  49.0  pounds 
calcium  carbonate. 

Nothing  will  be  gained  by  having  the  larger  divisions  of  the  co- 
ordinate paper  represent  less  than  one  per  cent,  silica  or  alumina 
and  five  pounds  of  calcium  carbonate,  since  the  small  spaces  will 
then  represent  o.i  per  cent,  and  technical  determinations  of  lime, 
silica  and  alumina  are  seldom  nearer  the  truth  than  this.  This 
will  keep  the  tables  well  down  in  size.  When  used  with  clays 
high  in  silica  space  can  be  saved  my  having  two  tables — one 
ranging  say  from  10-25%  and  serving  for  the  alumina  in  the  clay 
and  the  alumina  and  silica  in  the  marl,  the  other  ranging  say 
from  45  to  60%  for  the  silica  in  the  clay.  In  these  tables  two 
points  must  of  course  be  determined.  In  the  first  the  silica  line 
would  of  course  pass  through  the  point  of  intersection  of  the  ver- 
tical and  horizontal  lines  representing  10%  silica  and  10x5  or  50 
pounds  calcium  carbonate,  respectively,  and  the  point  of  intersec- 
tion of  the  vertical  and  horizontal  lines  representing  25%  silica 


PORTLAND 


and  25x5  or  125  pounds  of  calcium  carbonate,  respectively.  While 
in  the  second  table  it  would  pass  through  the  points  of  intersection 
of  the  vertical  line  representing  45%  silica  and  the  horizontal  line 
representing  45x5  or  225  pounds  of  calcium  carbonate,  and  of  the 
vertical  line  corresponding  to  60%  silica  and  the  horizontal  line 
corresponding  to  60x5  or  300  pounds  calcium  carbonate. 


Fig.  2.     Graphic  Method  for  Calculating  limestone. 

The  lines  may  of  course  be  drawn  to  represent  the  lime,  cal- 
cium oxide,  required;  in  which  event  the  main  vertical  divisions 
should  be  numbered  2,  4,  etc.,  and  have  twice  the  value  of  the 
spaces  on  the  horizontal  margin.  The  silica  line  would  in  this 
event  be  drawn  through  the  O,  O  point  and  the  point  of  intersec- 
tion of  the  vertical  line  corresponding  to  25%  silica  and  the  hori- 
zontal line  corresponding  to  25x2.8  or  70  pounds  calcium  oxide. 

The  above  table  shows  us  merely  the  amount  of  pure  carbon- 
ate of  lime  required  by  the  cement-rock  clay  or  shale.  To  find 
the  limestone  necessary  it  is  of  course  necessary  to  find  the  avail- 
able carbonate  of  lime  it  contains  by  the  above  chart  and  then 
calculate  the  quantity  to  be  added  as  shown  on  page  54.  The 


PROPORTIONING  RAW  MATERIAL  59 

following  table,  Fig.  2,  will  save  this  calculation  also,  however. 
A  large  piece  of  co-ordinate  paper  is  fastened  to  a  board  and  the 
main  divisions  on  the  lower  margin  are  numbered  10,  20,  30,  40 
etc.,  to  correspond  to  pounds  of  limestone.  Those  on  the  right 
and  left  hand  margins  are  numbered  10,  20,  30,  40,  etc.,  and  rep- 
resent pounds  of  calcium  carbonate  required  for  the  cement  rock. 
On  the  vertical  line  100,  the  main  divisions  are  numbered  10,  20, 
30,  etc.,  to  represent  pound  per  100  or  percentage  of  available 
calcium  carbonate  in  the  limestone.  A  ruler  is  fixed  so  as  to  turn 
about  the  O,  O  point.  The  pivot  around  which  the  rules  moves 
must  be  on  a  line  with  the  edge  of  the  ruler.  It  is  only  neces- 
sary to  set  the  edge  of  the  ruler  at  the  point  on  the  100  vertical 
line  (This  line  is  in  the  drawing  made  broad  but  it  would  be  bet- 
ter to  rule  over  it'  or  to  one  side  in  red  ink. )  representing  the  per- 
centage of  available  calcium  carbonate  in  the  limestone.  The  edge 
of  the  ruler  is  then  used  as  if  it  were  a  diagonal  line. 

To  find  the  number  of  pounds  of  a  limestone  equivalent  to  a 
given  weight  of  calcium  carbonate,  glance  along  the  horizontal 
line  corresponding  to  the  quantity  of  pure  calcium  carbonate  re- 
quired until  it  meets  the  ruler's  lower  edge.  The  corresponding 
reading  at  the  lower  margin  will  give  the  weight  of  limestone. 
For  example,  using  the  table,  we  wish  to  know  how  much  of  a 
limestone  containing  32.5  pounds  available  CaCO3  is  required  for 
a  cement  rock  that  requires  39.3  pounds  calcium  carbonate.  Set 
the  ruler's  lower  edge  so  it  intersects  the  100  vertical  line  at  32*. 5 
and  run  the  eye  along  the  horizontal  line  corresponding  to  39.3 
to  where  it  cuts  the  diagonal  line  which  passes  the  100  vertical 
line  at  32  (or  33),  and  then  down  the  nearest  vertical  line  to  the 
margin,  the  reading  here,  or  121,  will  be  the  weight  of  limestone 
needed. 

The  writer  has  used  in  his  work  a  formula  modeled  after  New- 
berry's,  which  is  given  below.  It  assumes  90  per  cent,  of  the 
theoretical  lime  needed  to  form  tri-calcium  silicate  and  tri-cal- 
cium  aluminate. 

Limestone  needed  per  ton  or  per  j  _(Ai  X  4.5  +  Bt  X  2.7)  —  C, 
pound  of  cement  rock  (or  clay)  J  ~~C2—  (A2  X  4.5  -f-  B2  X  2.7) 
When 


6O  PORTLAND  CEMENT 

A!  =  percentage  SiO2  in  the  cement  rock  or  clay 
Bj  =  A12O3  in  the  cement  rock  or  clay 

Cx  =  CaCO3  in  the  cement  rock  or  clay 

A2  =  SiO2  in  the  limestone  or  marl 

B2  =  A12O3  in  the  limestone  or  marl 

C2  =  CaCO2  in  the  limestone  or  marl 

Cement  mixtures  proportioned  by  this  formula  will  be  neither 
over  nor  underlimed  and  the  resulting  cement,  if  properly  burn- 
ed, will  give  good  strength  and  soundness  tests. 

This  will  be  found  as  near  a  general  formula,  applicable  to  all 
cases  and  material,  as  it  is  possible  to  get,  in  the  present  state  of 
our  knowledge  of  the  constitution  of  Portland  cement  clinker. 

Fixed  Lime  Standard. 

While  Newberry's  formula  is  very  useful  for  calculating  ce- 
ment mixtures  from  complete  analyses,  as  in  making  laboratory 
trial  burnings,  or  when  starting  up  a  new  mill,  or  opening  a  new 
deposit,  it  will  be  found  more  practicable  in  actual  mill  routine 
work,  to  fix  upon  a  certain  percentage  of  carbonate  of  lime  found 
to  give  satisfactory  results  by  experience  and  to  keep  the  mixture 
as  near  this  as  possible.  Provided  the  amount  of  water,  organic 
matter  and  magnesia  is  constant  in  raw  materials,  it  will  be  com- 
paratively easy  to  keep  a  pretty  uniform  mixture  by  merely 
watching  the  percentage  of  carbonate  of  lime.  In  the  cement- 
rock-limestone  mixtures  of  the  Lehigh  District  the  conditions  are 
pretty  constant  and  it  is  the  usual  practice  here  to  "control  the 
mix"  by  keeping  the  percentage  of  carbonate  of  lime  in  it  around 
a  fixed  point  (usually  74.5  to  75.5)  the  standard  varying  at  dif- 
ferent mills.  In  most  mills  using  limestone-clay  mixtures,  very 
much  the  same  conditions  obtain,  the  magnesia  and  water  re- 
maining fairly  constant  and  organic  matter  being  present  only  in 
very  small  percentages.  Some  clays  show  considerable  variations 
in  different  parts  of  the  bed  in  the  relative  proportions  of  the  silica 
and  the  alumina  to  each  other.  In  this  event  the  clay  should  be 
so  worked  as  to  give  a  constant  ratio  between  the  silica  and  the 
alumina.  By  doing  this  a  constant  lime  standard  may  be  held  to, 
and  a  cement  of  more  uniform  setting  properties  will  result.  In 
the  marl-clay  mixtures  water  and  organic  matter  are  apt  to  vary 


PROPORTIONING  RAW  MATERIAL  6l 

widely,  and  in  order  to  make  a  uniform  mix  it  is  necessary  to  do 
more  than  merely  determine  the  lime  in  the  slurry,  as  the  wet 
mixture  of  marl  and  clay  is  called.  When  the  organic  matter  is 
constant  it  is  merely  necessary  to  dry  the  mixture  and  determine 
the  carbonate  of  lime  as  in  a  limestone-cement  rock  or  limestone- 
clay  mixture.  In  controlling  the  mixture  by  a  carbonate  of  lime 
determination  it  is  necessary  that  the  ratio  between  the  silica  and 
alumina  be  kept  constant,  this  can  usually  be  done  without  diffi- 
culty after  a  thorough  prospecting  of  the  raw  materials.  This 
problem  will  usually  be  simplified  by  having  the  quarrying  opera- 
tions spread  out  over  the  whole  face,  and  on  several  ledges,  and 
not  confined  to  one  particular  spot.  For  instance,  suppose  a 
quarry  to  have  a  face  of  100  ft.  and  a  depth  of  48  ft.  and  to  be 
worked  in  benches  of  16  ft.  each.  It  will  be  a  simpler  matter  to 
keep  a  constant  ratio  between  the  silica  and  the  alumina  by  dis- 
tributing the  quarry  force  over  the  whole  face  taking  rock  from 
several  benches  than  it  would  be  by  localizing  the  work  with  a 
steam  shovel  at  one  point. 

Formulas  for  a  Fixed  Lime  Standard. 

The  mathematical  part  of  calculating  cement  mixtures  for  a 
fixed  lime  standard  may  be  simplified  by  the  following  formulas, 
which  have  been  used  by  the  writer  in  his  work  and  found  useful. 

The  first  formula  is  for  use  when  the  cement  rock  is  weighed 
and  the  proper  proportion  of  this  weight  of  limestone  is  added. 

i.  To  find  the  percentage  of  a  given  limestone  to  be  added  to 
a  given  cement-rock  or  clay  to  make  a  given  mixture 

Let— 

X  =  Percentage  of  limestone  necessary. 
L  =  Percentage  of  CaCO3  in  the  Limestone. 
R  =  Percentage  of  CaCO3  in  the  Rock  or  Clay. 
M  =  Percentage  of  CaCO3  desired  in  the  Mixture. 

Then— 

M  —  R 


Example  —  What  percentage  of  limestone  analyzing  95  per 
cent.  CaCO3  must  be  added  to  a  cement  rock  analyzing  70  per 
cent.  CaCO3  to  give  a  mix  analyzing  75  per  cent.  CaCO3  ? 


62  PORTLAND  CEMEN1 

Percentage  of  limestone  =  —  -  —  X  100  =  5^—  2c 

95  —  75  20 

Hence,  to  every  100  Ibs.  of  cement  rock  25  Ibs.  of  limestone 
must  be  added. 

The  next  formula  is  practically  the  same  as  the  last  only  it  is 
intended  for  use  when  the  limestone  or  marl  is  weighed  and  the 
proper  proportion  of  this  weight  of  clay  or  shale  is  added. 

2.     To  find  the  percentage  of  a  given  clay  or  shale  (or  cement 
rock)  to  be  added  to  a  given  marl  or  limestone  to  make  a  given 
mixture. 
Let— 

X  =  Percentage  of  Clay  or  Shale  necessary. 
C  =  Percentage  of  CaO  in  Clay  or  Shale. 
L  =  Percentage  of  CaO  in  Marl  or  Limestone. 
M  =  Percentage  of  CaO  desired  in  the  mixture. 
Then— 


Example  —  What  percentage  of  clay  analyzing  2.5  per  cent. 
CaO  must  be  added  to  a  limestone  containing  53  per  cent.  CaO  to 
obtain  a  mixture  analyzing  41.0  per  cent.  CaO? 


Percentage  clay  =  X  100  =     ~  =  31 

41  —  2-5  3°-5 

Instead  of  percentages  of  CaO  percentages  of  CaCO3  may  be 
used,  but  if  used  in  one  case,  it  must  be  used  in  all. 

It  sometimes  happens  that  it  is  more  convenient  to  divide  the 
mix  into  percentages  of  limestone  and  of  cement  rock  or  clay  than 
to  make  one  constituent  a  certain  percentage  of  the  other.  For 
example,  when  both  the  limestone  and  cement  rock  are  already 
in  storage  and  both  are  weighed  into  the  same  hopper,  it  makes 
fewer  dumps  necessary,  to  fill  the  hopper  full  each  time  and  to  so 
proportion  the  limestone  and  clay  as  to  just  do  this.  The  follow- 
ing formula  will  give  the  percentage  of  both  the  calcarious  and 
argillaceous  constituents  of  the  mixture. 

j.  To  find  the  percentage  of  a  given  cement  rock  and  of  a 
given  limestone  for  a  given  mix. 


PROPORTIONING  RAW  MATERIAL  63 

Let— 

X  —  Percentage  of  Cement  Rock,  Shale  or  Clay. 

Y  =  Percentage  of  Limestone  or  Marl. 

R  =  Percentage  of  CaCO3  in  Cement  Rock,  Shale  or  Clay. 

L  =  Percentage  of  CaCO3  in  Limestone  or  Marl. 

M  =  Percentage  of  CaCO3  desired  in  Mixture. 
Then— 


or  X  =  100  —  Y 
Y  =  100  —  X 

Example  —  What  percentage  of  limestone  analyzing  0,5  per  cent. 
CaCO3  and  of  cement  rock  analyzing  70  per  cent.  CaCO3  are  re- 
quired in  a  mixture  to  analyze  75  per  cent.  CaCO3  ? 


7  s  —  ?o 

Percentage  limestone  ==«        -  X  100  =  -  —  =20 

95  —  70  25 


/-N  (-  _  fj  g»  OOOO 

Percentage  cement  rock  =  —  --  —  X  100  ==  —    -  =  80 

95  —  70  25 

To  illustrate  a  case  where  these  formulas  are  applicable,  let  us 
suppose  that  our  hopper  holds  10,000  Ibs.,  then  10,000  X  -20  or 
2,000  Ibs.  of  this  must  be  limestone  and  10,000  X  -80  or  8,000 
Ibs.,  must  be  cement  rock.  . 

As  another  example,  let  us  suppose  that  at  a  four  kiln  plant 
there  are  say  six  men  wheeling  limestone  and  cement  rock  from 
separate  piles  to  the  crusher,  and  that  each  barrow  holds  a  maxi- 
mum of  500  Ibs.,  while  the  six  in  rotation  per  trip  usually  handle 
2,500  Ibs.  Now,  20  per  cent,  of  2,500  Ibs.  is,  of  course,  500  Ibs., 
and  80  per  cent,  is  2,000,  so  that  there  must  be  500  Ibs.  of  lime- 
stone for  every  2,000  Ibs.  of  cement  rock.  By  putting  two  men 
on  the  limestone  pile  and  setting  their  scale  at  250  Ibs.  and  four 
men  on  cement  rock  with  their  scale  set  at  500  Ibs.,  the  mix  will 
be  kept  in  proper  proportion. 

After  the  mixture  has  been  made  and  checked,  if  it  is  desired  to 
correct  that  which  has  been  already  ground,  the  two  formulas 


64  PORTLAND 

first  given,  as  the  case  may  require,  may  be  used.  If  the  mix 
analyzes  too  low  and  limestone  is  needed  the  first  formula  must 
be  used.  If  too  high  and  clay  is  called  for  the  second  formula  will 
give  the  amount. 

Unfortunately  in  many  mills  no  provision  is  made  for  correct- 
ing the  mix  after  it  leaves  the  grinders  and  the  efforts  of  the 
chemist  are  directed  merely  to  making  the  subsequent  mix  all 
right.  The  formula  given  below  is  for  use  here  and  gives  the 
correct  amount  of  limestone  for  the  new  mixture./ 

4.     To  calculate  the  correct  percentage  of  limestone  to  be  add- 
ed to  a  cement  rock  from  the  result  of  a  former  mixture  of  the 
two. 
Let— 

M  —  Percentage  of  CaCO3  desired  in  mixture. 
F  =  Percentage  of  CaCO3  found  in  mixture. 
A  =  Percentage  of  Limestone  already  added. 
L  =  Percentage  of  CaCO3  in  Limestone. 
X  =  Corrected  Percentage  of  Limestone  needed  to  make  the 

mixture  analyze  M  per  cent.  CaCO3. 
Then— 

(M-F)   (IOQ  +  A) 

L-M 

Example  I.  —  The  mixture  analyzes  74.5  and  should  analyze 
75.0  per  cent.  CaCO3.  20  per  cent,  (of  the  weight  of  the  cement 
rock)  of  limestone  analyzing  95  per  cent.  CaCO3  was  added. 
What  amount  should  be  added? 

x  =  2Q  +  (75  ~  74.5)    ioo  +  20)=  2f     0.5^020  =  2Q      jo_ 
95  —  75  20  20 

=  23  per  cent. 

Example  2.  —  The  mixture  analyzes  76.0  per  cent.  CaCO3  and 
should  analyze  75.0  per  cent.  CaCO3.  If  20  per  cent,  of  95  per 
cent,  limestone  has  been  added,  to  what  should  this  be  reduced? 
-  =  -1X120 


95  -  75  20 

14  per  cent. 

Where  clay  is  added  to  limestone  or  marl  and  where  formula 
2  has  been  used  to  calculate  the  mix  then  formula  4  becomes  as 
follows  : 


PROPORTIONING  RAW   MATERIAL,  65 

5.  To  calculate  the  correct  percentage  of  clay  or  shale  to  be 
added  to  a  limestone  or  marl  from  the  result  of  a  former  mixture 
of  the  tivo. 

Let— 

M  =  Percentage  of  CaO  desired  in  Mixture. 

F  =  Percentage  of  CaO  found  in  the  Mixture. 

B  =  Percentage  of  Clay  already  added. 

C  —  Percentage  of  CaO  in  Clay. 

X  —  Corrected  Percentage  of  Clay  needed  to  make  the  mix- 

ture analyze  M  per  cent.  CaO. 
Then— 

(M-F)   (IOQ  +B) 

-F=C" 

When  it  is  customary  to  divide  the  mix  into  percentages  and 
where  formulas  No.  3  have  been  used  to  calculate  the  mix  the 
formula  given  below  will  arrive  at  the  corrected  percentages  of 
cement  rock  and  of  limestone. 

6.  To  calculate  the  correct  percentage  of  limestone  and  of  ce- 
ment rock  in  a  mixture  from  the  result  of  a  former  mixture. 

Let— 

M  —  Percentage  of  CaCO3  desired  in  mixture. 

F  =  Percentage  of  CaCO3  found  in  mixture. 

A  =  Percentage  of  Limestone  already  in  mixture. 

L  =  Percentage  of  CaCO3  in  the  Limestone. 

X  —  Corrected  Percentage  of  Limestone  to  make  the  mix- 

ture analyze  M  per  cent.  CaCO3.  . 
Then— 

(M  —  F)   (IPO  —  A) 

~ir=¥~ 

Y=  loo  —  X 

Example  —  The  mixture  analyzes  74.5  and  should  analyze  75.0. 
The  mixture  is  composed  of  20  per  cent,  limestone  analyzing  95 
per  cent.  CaCO3,  80  per  cent,  cement  rock.  What  are  the  cor- 
rect proportions? 


95  —  74-5  20.5 

Y  =  100  —  22  =  78 


66  PORTLAND  CEMENT 

In  formula  No.  6  it  is  assumed  that  the  percentage  of  CaCO3 
in  the  limestone  is  correct  and  that  the  error  in  the  mix  causing 
it  to  be  74.5  instead  of  75.0  CaCO3  is  due  to  the  failure  to  prop- 
erly sample  the  cement  rock.  If  clay  is  added  to  rock  or  lime- 
stone for  the  mixture  it  is  better  to  assume  the  clay  to  be  correct, 
in  which  case  we  have  the  following: 

/.     To  calculate  the  percentage  of  clay  or  shale  and  of  lime- 
stone or  marl  in  a  mixture  from  the  result  of  a  former  mixture, 
Let— 

M  =  Percentage  of  CaO  desired  in  Mixture. 

F  =  Percentage  of  CaO  found  in  Mixture. 

B  =  Percentage  of  Clay  or  Shale  already  in  Mixture. 

C  =  Percentage  of  CaO  in  Clay  or  Shale. 

Z  =  Correct  Percentage  of  Clay  or  Shale  in  the  Mixture  to 

make  it  analyze  M  per  cent.  CaO. 
X  =  Corrected  Percentage  of  Limestone  or  Marl. 
Then— 

(F-M)  (loo-B) 

F-C 

X—  TOO  — Z 

Example. — The  mixture  analyzes  40.5  and  should  analyze  41.0 
per  cent.  CaO.  The  mixture  is  composed  of  24  per  cent,  clay  and 
76  per  cent,  limestone.  Clay  analyzes  3  per  cent.  CaO.  What 
are  the  correct  proportions? 


40-5-3  37-5 

=  23  per  cent. 
X  =  loo—  23  =•  77 

A  slide  rule  will  greatly  facilitate  rapid  calculation  of  cement 
mixture  and  changes  to  be  made  in  the  same. 

A  lo-inch  one  can  be  bought  for  as  little  as  $1.25  and  will  be 
found  to  come  in  very  handy  for  other  laboratory  calculations 
where  accuracy  is  not  required  to  more  than  three  figures,  such  as 
figuring  out  the  percentage  of  sulphuric  anhydride  and  magnesia 
in  an  analysis. 

A   simple   table  of   the   quotients  of  - —  —  or  -± — '  which 

L  —  M       M  —  C 


PROPORTIONING  RAW  MATERIAL 


67 


ever  is  used,  will  greatly  aid  calculations.     Formula   i  will  then 


become  X  =  (M  —  R)  Q  when  Q  = 
be  X  —  (L  —  M)  R  where  R  == 


100 


L  — M 

IOO 


,  and  formula  2  will 


.     Below  is  given  such  a 

table  for  a  mix  desired  to  contain  75  per  cent.  CaCO3,  and  for 
limestone  ranging  from  92  to  98  per  cent  CaCO3. 

Values  of  Q,  Mixture  =  75.0  per  cent.  CaCO3. 


Per  Cent.  CaCO3  in  I«ime- 

stone. 

Q 

Per  Cent.  CaCO3  in  lyime- 
stone. 

Q 

92.O 

5-9 

95-5 

4-9 

92.5 

5-7 

96.0 

4-8 

93-o 

5-6 

96.5 

4-7 

93-5 

5-4 

97.0 

4-5 

94.0 

5-3 

97-5 

4.4 

94-5 

5-i 

98.0 

4-3 

95-0 

5-o 

98.5 

4-2 

Using  this  table  in  the  example  given  under  i. 

Percentage   of   Limestone  =  (75-70)  X  5  =  25. 
Controlling  the  Mixture  in  the  Wet  Process. 

For  controlling  the  mixture  in  mills  using  marl  and  clay  and 
consequently  the  wet  process,  many  methods  are  in  vogue.  At 
some  of  the  plants  the  slurry  is  merely  dried  and  the  carbonate  of 
lime  determined  in  the  usual  manner  as  outlined  in  Chapter  X, 
either  by  titration  with  standard  N/2  acid  and  alkali  or  by  meas- 
uring the  volume  of  carbon  dioxide  liberated  in  the  Scheibler's 
calcimeter.  Another  plan  and  one  which  is  in  use  in  the  laboratory 
of  the  Omega  Portland  Cement  Co.,  Jonesville,  Mich.,  is  to  de- 
termine the  lime  by  titration  with  standard  N/2  acid  and  alkali, 
and  also  "the  silicates."  The  determination  of  the  latter  is  also 
given  in  the  chapter  on  "The  Analysis  of  the  mix."  The  ratio  be- 
tween the  silicates  and  the  lime  is  then  kept  constant.  In  a  sample 
of  correctly  proportioned  slurry  upon  which  this  determination 
was  made,  the  ratio  was  3.8.  This  ratio  undoubtedly  will  vary  at 


68  PORTLAND  CEMENT 

different  mills,  and  also  with  any  variations  in  the  manner  of  car- 
rying out  the  determination  of  the  silicates,  so  that  this  ratio  must 
be  fixed  by  experience.  At  a  new  mill  it  could  be  determined  to 
some  extent  before  beginning  operations  by  making  up  a  set  of 
"standard  samples"  (using  Newberry's  modified  formula  to  de- 
termine the  proper  proportions)  from  various  lots  of  marl  and 
clay.  The  marl  for  these  samples  should  be  so  selected  as  to 
cover  the  range  expected  to  be  met  with  in  practice.  This  applies 
to  the  clay  also.  The  ratios  between  the  lime  and  the  silicates 
should  then  be  determined  and  if  found  fairly  constant  it  can  be 
adopted.  If  possible  these  samples  should  be  checked  by  burn- 
ing in  a  small  kiln  and  examining  the  properties  of  the  resulting 
cement.  It  may  be  found  necessary  after  starting  up  the  mill  to 
raise  or  lower  this  ratio. 

At  the  two  mills  of  the  Sandusky  Portland  Cement  Co.,  the  mix 
is  controlled  by  the  ratio  between  the  percentage  of  lime,  deter- 
mined by  acid  and  alkali,  and  the  percentage  of  "insoluble,"  as 
determined  by  boiling  one  gram  for  5  minutes  with  10  per  cent, 
hydrochloric  acid,  filtering,  washing,  igniting  and  weighing.  This 
ratio  is  also  different  for  different  works.  At  the  Sandusky  plant 
of  the  above  company  the  ratio  is  about  3.9  and  at  the  Syracuse, 
Ind.,  mill  4.2,  the  difference  being  due  to  a  greater  amount  of 
carbonate  of  magnesia  and  'a  more  silicious  clay  at  the  latter  mill. 
This  ratio  must  be  fixed  like  the  lime-silicate  ratio  by  compari- 
son with  samples  carefully  analyzed. 

The  author  suggests  the  following  method  of  control  as  doing 
away  with  the  uncertainties  due  to  water  and  organic  matter  in 
the  slurry.  Measure  into  a  large  weighed  platinum  crucible  such 
a  quantity  of  wet  slurry  as  will  give  about  0.8  gram  of  dried 
slurry  (or  that  amount,  0.8  gram,  direct  of  dried  slurry).  Dry 
rapidly,  avoiding  any  large  loss  by  spattering  if  necessary,  ignite 
cautiously  at  first,  then  strongly  for  5  minutes  over  a  Bunsen 
burner,  and  then  for  10-15  minutes  over  a  blast.  The  result  will 
be  a  clinker  of  practically  the  same  composition  as  that  obtained 
in  the  kiln  except  that  it  lacks  the  fuel  ash.  The  crucible  and 
contents  are  then  weighed  and  the  weight  of  the  clinker  calcu- 
lated. The  lime  is  then  determined  in  this  clinker  by  the  rapid 
permanganate  method  given  in  Chapter  IX.  This  gives  an  ex- 


PROPORTIONING  RAW  MATERIAL  69 

cellent  check  on  the  slurry,  if  the  magnesia  is  anywhere  near 
constant,  as  it  is  only  necessary  to  keep  the  lime  in  this  clinker 
around  a  constant  figure.  The  sample  of  wet  slurry  may  be  rap- 
idly dried,  in  the  crucible,  in  the  following  manner :  Incline  the 
crucible  on  a  tripod  over  a  burner  turned  low,  in  such  a  way  that 
the  flame  plays  under  the  upper  part  of  the  crucible.  This  will 
cause  a  rapid  evaporation  of  the  water.  When  the  mass  looks 
dry  the  burner  can  be  moved  back  gradually  until  it  plays  upon 
the  mass  directly  and  allowed  to  remain  here  5  minutes  when  the 
crucible  is  ready  for  the  blast.  The  lime  will  be  somewhat  higher 
in  this  artificially  prepared  clinker,  than  in  that  from  the  kilns, 
owing  to  the  contamination  of  the  latter  by  the  fuel  ash,  and  still 
higher  in  lime  than  the  finished  cement  in  which  it  is  lowered  by 
the  addition  of  gypsum  and  the  absorption  of  water  from  the  air. 
What  the  lime  should  be  in  the  clinker  can  easily  be  determined 
by  applying  the  method  to  standard  samples. 

In  making  the  mixture  with  wet  materials  such  as  clay  and 
marl  the  water  and  organic  matter  are  disturbing  elements.  In 
order  to  make  the  mixture  with  these  materials  it  is  necessary  to 
determine  the  percentage  of  water  they  contain,  and  from  this  to 
calculate  the  weight  of  wet  marl  or  clay  equal  to  a  given  weight 
of  dry  material.  For  instance,  suppose  the  marl  to  contain  60 
per  cent,  water  and  the  clay  15  per  cent.  Then  100  Ibs.  of  wet 
marl  would  only  contain  100-60  or  40  Ibs.  dry  marl,  and  from  the 
proportion 

(40:ioo::ioo:X) 

We  find  250  Ibs.  of  wet  marl  are  equivalent  to  100  of  dry  marl. 

If  100  Ibs.  of  dry  marl  require  31  Ibs.  of  dry  clay,  it  would  re- 
quire 36.4  Ibs.  of  wet  clay  by  a  similar  calculation.  So  that  our 
proportions  would  be  250  of  wet  marl  to  36.4  of  moist  clay. 

This  will  apply  to  the  use  of  any  of  the  formulas  given  in  this 
chapter,  when  used  for  calculations  involving  wet  materials.  The 
results  will  be  in  pounds  of  dry  material  and  must  then  be  calcu- 
lated to  wet  marl,  clay  or  slurry.  In  using  the  ratio  between  either 
the  lime  and  the  silicates  or  the  lime  and  insoluble.  The  lime  and 
the  silicates  must  be  found  in  the  marl,  and  the  silicates  (and  lime 
if  any)  in  the  clay,  if  the  first  method  is  used;  and  the  lime  and 
the  insoluble  in  the  marl,  and  the  insoluble  and  lime,  if  any,  in  the 


7O  PORTLAND  CEMENT 

clay,  if  the  second  method  is  to  be  used,  in  order  to  proportion 
the  two.    The  following  formula  will  give  the  proper  proportions 
of  clay  and  marl  to  make  a  slurry  of  a  given  ratio. 
Let— 

L  =  Lime  in  the  Marl. 

1  =  Lime  in  Clay. 

S  =  Silicates  (or  Insoluble)  in  Marl. 

s  =  Silicates  (or  Insoluble)  in  Clay. 

Lime 

=  Silicate  (or  Insoluble) 
Then— 

Marl_    R  XS  — 1 

Clay  ~~  L  —  R  X  S 

This  formula  may,  of  course,  be  used  to  correct  a  slurry  found 
to  be  too  high  or  low  in  lime.  In  this  event,  if  the  clay  is  called 
for,  the  lime  and  silicates  in  the  slurry  should  be  represented  by 
L  and  S,  but  if  marl  is  needed,  by  1  and  s. 


CHAPTER  V. 


QUARRYING,  EXCAVATING,  DRYING  AND  MIXING 
THE  RAW  MATERIAL. 


Quarrying  the  Stone. 

Limestone,  cement-rock  and  shale  are  usually  quarried,  while 
clay  is  dug  from  pits  and  marl  is  dredged,  often  from  under 
water.J  Deposits  of  cement  rock  and  limestone  are  usually  over- 
laid by  a  few  feet  of  soil  and  clay  which  must  be  removed  by 
scrapers  or  shoveling.  When  clay  is  used  to  make  the  mix,  this 
surface  deposit  is  conveyed  to  the  mill,  otherwise  it  is  carted  away 
to  a  dump.  In  one  or  two  quarries,  notably  that  of  the  Lawrence 
at  Siegfried,  Pa.,  it  has  been  necessary  to  mine  the  stone,  owing 
to  the  dip  of  the  material,  which  carries  down  under  other  rock. 
This  method  rarely  pays,  however,  as  in  order  to  meet  competi- 
tion, it  is  necessary  to  deliver  the  rock  to  the  mill  at  a  lower  cost 
than  will  permit  of  mining.  Some  deposits  of  rock  and  limestone 
are  so  situated  that  they  can  be  opened  on  a  hillside,  at  others,  it 
has  been  necessary  to  go  straight  down. 

The  stone  is  usally  blasted  down  in  benches,  sometimes  along 
the  whole  face  of  the  quarry  at  once,  at  others,  only  a  small  part 
of  a  bench  at  a  time.  The  drill  holes  for  the  blasting  are  usually 
made  with  power  drills,  run  by  steam  or  compressed  air,  and  are 

rried  to  a  depth  of  16  to  20  feet.  In  blasting,  an  effort  is  made 
to  shatter  the  rock  as  much  as  possible,  in  order  to  save  subse- 
quent sledging  and  blasting  to  break  up  the  big  pieces.  In  sprite 
of  this  attempt  it  is  necessary  at  practically  all  of  the  quarries(  ex- 
cept that  of  the  Edison  Portland  Cement  Co!,  to  break  up  some 
big  pieces  of  rock  either  with  dynamite  or  hand  sledges.  It 
seems  curious,  in  this  connection,  that  no  one  has  tried  the  use  of 
air  hammers  to  do  this  work.  They  would  be  much  cheaper  than 
hand  sledging  and  would  undoubtedly  break  up  the  rock. 

Where  many  large  rocks  have  to  be  broken  up  by  dynamite,  a 
small  hand  air  drill  will  be  found  more  convenient  for  this  pur- 


72  PORTLAND  CEMENT 

pose  than  anything  else.  These  drills  can  be  attached  to  a  long- 
piece  of  strong  flexible  hose  coupled  to  the  air  line  and  used  to 
drill  rocks  in  any  part  of  the  quarry.  In  a  minute's  time  a  hole 
a  foot  deep  can  be  drilled  in  cement  rock,  and  this  can  then  be 
filled  with  dynamite  and  the  rock  shattered. 

After  breaking  up  to  a  size  suitable  for  crushing  and  loading, 
^  the  rock  is  ready  for  the  mill. 

In  some  quarries  the  rock  is  loaded  on  carts  and  carried  to  a 
point  out  of  danger  from  the  blasting  and  dumped  into  side  dump 
cars  which  are  hauled  to  the  mill  up  an  incline  by  a  cable  hoist. 
At  other  mills,  temporary  tracks  are  laid  from  a  turn-table  or 
switch  at  the  face  of  the  incline  to  the  rock  piles,  and  the  cars 
are  loaded  direct  from  these,  and  then  hauled  to  the  mill  as  before. 
When  the  quarrying  has  been  carried  straight  down,  the  rock  is 
loaded  on  skips,  which  are  carried  to  the  mill  by  an  serial  cable 
and  hoist.  The  cars  are  loaded  by  hand  at  nearly  all  cement  mills 
and  a  great  deal  of  sledging  is  necessary  in  order  to  reduce  the 
rock  to  a  size  suitable  for  handling  and  crushing.  At  a  few  of  the 
larger  mills  steam  shovels  are  used,  but  they  interfere  to  some 
extent  with  blasting  and  the  crushers  at  most  of  the  mills  are  too 
small  to  take  the  rock,  as  it  comes  from  the  pile,  without  being 
broken  up.  Then,  too,  unless  the  deposit  is  very  regular  the  steam 
shovels  localize  the  quarrying  so  that  the  cement  is  not  so  uni- 
form as  if  a  large  face  were  worked.  Nevertheless,  it  is  probable 
that  they  will  be  introduced  gradually,  in  connection  with  either 
larger  crushers  or  some  form  of  air  or  steam  hammer  to  break 
up  the  large  pieces  of  rock  in  the  quarry,  and  that  the  chemist 
will  be  expected  to  work  out  a  way  around  the  difficulty  of  an 
irregular  composition. 

When  the  material  is  of  a  regular  composition  such  as  is  often 
the  case  with  limestone,  shale  or  clay,  steam  shovels  can  be  used 
to  advantage  and  on  the  latter  two  classes  of  material  are  used 
to  some  extent.  As  clay  is  soft  the  steam  shovel  can  both  dig 
out  the  clay  and  load  it  on  the  cars.  Usually  it  is  necessary  to 
carry  the  clay  some  distance,  for  the  mill  is  always  located  as 
near  the  marl  or  limestone  as  possible,  as  four  or  five  times  as 
much  of  these  are  used  as  of  clay  or  shale. 


QUARRYING,  EXCAVATING,  ETC.,  OF  RAW   MATERIAL  73 

Excavating  Marl. 

Marl  as  has  been  said  carries  considerable  water  and  the  de- 
posits usually  lie  in  depressions  and  underneath  the  surface  of  a 
shallow  lake  or  marsh.  In  some  instances,  the  marl  deposit  is 
overlaid  by  a  foot  or  more  of  peat  which  must  be  dredged  off.  In 
excavating  the  marl  several  plans  are  followed,  one  of  the  most 
common  is  that  of  a  steam  dredge  mounted  on  a  barge  which 
scrapes  up  the  marl  from  the  bottom  of  the  lake  and  loads  it  on 
barges.  These  barges  are  then  towed  to  the  wharf  and  unloaded 
by  machinery  on  belt  conveyors  which  carry  the  marl  to  the  mill. 
This  can,  of  course,  be  done  only  where  the  marl  lies  under  water. 
When  the  beds  have  been  drained,  it  is  usual  for  the  steam  dredge 
or  shovel  to  float  on  its  barge,  in  the  channel  which  it  cuts  out  of 
the  marl,  and  to  load  the  marl  on  to  cars,  running  on  temporary 
tracks,  on  a  bank  by  the  barge.  The  channel  fills  with  ground 
water  and  the  bank  is  thrown  up  by  the  dredge  either  from  the 
stripping  on  top  of,  or  the  material  underneath  the  marl.  Instead 
of  using  barges  and  cars  to  convey  the  marl  to  the  mill  some  of 
the  Michigan  mills  drop  their  marl  from  the  scoop  of  the  dredge 
into  the  hopper  of  a  pug  mill  on  a  boat  or  car.  Here  the  marl  is 
mixed  with  water  to  form  a  thin  mud,  which  is  pumped  to  the 
mill  through  a  pipe  line,  carried  over  the  marsh  or  marl  bed  on  a 
wooden  trestle.  The  steam  dredges  are  of  the  same  type  as  those 
used  for  excavating  cuts  by  railroads  and  for  deepening  the  chan- 
nels of  rivers  and  harbors.  They  consist  of  a  scoop  or  dipper 
having  a  hinged  bottom  and  fixed  to  a  long  arm.  This  arm  can 
be  swung  to  either  side,  raised,  lowered  or  pushed  forward,  by  a 
system  of  chains,  racks  and  pinions.  Some  of  the  dredges  are  of 
the  orange  peel  bucket  type.  These  have  a  bucket  hanging  from  a 
revolving  arm  by  cables  or  chains,  which  opens  and  shuts  and  is 
filled  by  lowering  to  the  bottom  of  the  lake  open  and  then  closing. 
Fig.  3  shows  a  steam  dredge  such  as  is  used  in  excavating  marl. 

The  pug  mills,  Fig.  4,  used  in  cement  works  are  similar  to 
those  used  in  the  better  equipped  brick  yards,  and  consist  of  d, 
long  steel  cylinder,  in  which  revolve  two  shafts  provided  with 
steel  blades.  The  mixture  of  marl  and  clay  enters  at  one  end  and 
is  forced  out  at  the  other.  During  its  passage  it  is  churned  up  by 


QUARRYING,  EXCAVATING,  ETC.,  OF  RAW   MATERIAL 


75 


the  blades  and  thoroughly  mixed.  When  the  marl  is  pumped  from 
the  lake  to  the  mill,  it  is  usual  to  locate  a  separator  on  the  barge 
to  take  out  the  sticks,  roots,  etc.  This  consists  usually  of  a  per- 
forated screen  through  which  the  marl  is  forced.  The  separator 
also  serves  as  a  pug  mill  in  reducing  the  marl  to  a  uniform  paste. 
The  best  system  of  pumping  marl  is  with  compressed  air.  In 
this  system  of  pumping,  there  are  two  cylinders  located  side  by 


O 


Fig.  4.     Pug  Mill  (Bonnot  Co.) 

side,  both  of  which  are  connected  with  the  air  compressor.  One 
of  these  cylinders  is  being  drawn  full  of  slurry  by  the  compressor 
while  the  other  is  being  emptied.  When  used  for  pumping  marl 
to  the  mill  the  cylinders  and  air  compressor  are  located  on  the 
barge.  Fig.  5  shows  this  system  and  Fig.  6  illustrates  a  ball  valve 
plunger  slurry  pump  which  was  manufactured  by  the  Bonnot  Co. 
Its  action  is  similar  to  that  of  other  pumps  and  is  evident  from  the 
cut. 

Stone  Houses. 

In  mills  using  the  dry  process,  the  rock  goes  from  the  quarry 
to  a  stone  house.  Here  it  is  treated  in  one  of  four  ways : 

i.  It  is  dumped  directly  into  large  piles,  which  are  then  analy- 
zed, and  from  this  analysis  the  necessary  limestone  or  clay  to  be 
added  is  calculated.  The  rock  is  then  loaded  on  buggies  or  bar- 
rows and  wheeled  to  the  crusher  after  being  weighed,  where  it 
meets  another  buggy  or  barrow  loaded  with  the  calculated 
amount  of  limestone  or  clay.  The  two  barrows  are  then  dumped 
into  the  crusher  together,  or  one  after  the  other.  In  some  mills 


PORTLAND  CEMENT 


using  cement  rock,  the  rock  is  not  weighed  before  being  dumped 
and  the  barrows  are  then  merely  averaged  as  weighing  so  much. 
The  limestone  is  then  averaged  also  and  proportioned  somewhat 
in  this  manner,  two  barrows  of  rock  to  one  barrow  of  limestone, 
etc. 


.-  PUMP  TANKS 


—  WATC&  SUPPL  Y 


Fig.  5.    Harris  System  of  Pumping  Marl  by 
Compressed  Air. 


Fig.  6.     Ball  Valve  Slurry  or  Marl 
Pump. 


2.  The  rock  may  be  weighed  as  it  comes  from  the  quarry  and 
the  proper  amount  of  limestone  or  clay,  as  calculated  from  quarry 
analysis,  added.  Part  of  the  cars  are  then  dumped  into  the  crush- 
er and  the  others  are  dumped  into  a  pile  for  night,  when  it  is 
necessary  to  wheel  from  these  to  the  crusher  with  barrows,  etc. 
At  several  mills  all  the  cars  are  dumped  into  the  crusher,  part  of 
the  stone  going  to  the  mill  and  part  of  it  being  stored  in  bins  for 
the  night.  The  rock  is  drawn  from  the  bins  upon  belt  conveyors 
running  to  the  mill. 


QUARRYING,  EXCAVATING,  ETC.,  OF  RAW   MATERIAL  77 

3.  The  rock  is  dumped  into  the  crusher  and  conveyed  into  bins, 
where  it  remains  until  the  bins  are  analyzed,  when  it  is  draAvn  out 
and  mixed  with  a  proper  amount  of  crushed  limestone  or  clay 
held  in  another  bin. 

4.  A  better  way  than  any  of  the  above,  is  to  pass  the  rock 
and  limestone  through  the  ball  mills  and  grind  to  a  fineness  of 
say  10  to  i8-mesh,  store  in  separate  bins  of  6  or  more  hours  ca- 
pacity, analyze  each  bin  and  then  make  the  mixture  of  the  two 
accordingly.    This  is  a  particularly  desirable  way,  in  the  case  of 
a  clay  and  limestone  mixture,  as  segregation  of  the  two  can  not 
occur  in  the  tube  mills  as  both  are  finely  ground  and  the  mixture 
of  clay  and  limestone  is  a  homogeneous  one.  In  piling  rock  either 
in  bins  or  piles,  the  coarse  pieces  will  roll  down  the  sides  and  the 
fine  ones  remain  in  the  centre  of  the  pile.    In  drawing  from  such 
a  pile,  it  is  a  hard  matter  not  to  start  with  fine  and  wind  up  with 
coarse  particles  if  the  drawing  is  done  from  the  centre,  or  in 
working  in  from  the  edge  of  the  pile,  not  to  start  with  coarse  par- 
ticles and  wind  up  with  fine.    As  in  a  cement  rock-limestone  mix 
the  finer  particles  are  apt  to  be  the  soft  cement  rock  and  the 
coarser  ones  the  hard  limestone  the  difficulty  ^  of  keeping  a  uni- 
form mix  by  the  methods  now  in  vogue  will  be  understood.     In 
few  of  the  mills  of  the  Lehigh  District  has  any  great  amount  of 
thought  been  expended  to  aid  the  chemist  in  making  a  uniform 
mix  (the  usual  thing  sought  being  merely  economy  in  handling 
the  rock),  and  it  is  to  the  credit  of  the  chemists  of  this  region, 
working  on  such  variable  material  as  cement  rock,  that  the  Le- 
high Valley  brands  hold  the  position  they  do. 

The  mechanical  equipment  of  the  stone  house  usually  consists 
of  the  crushers  and  dryers.  The  former  are  usually  of  the  Gates 
gyratory  rock-breaker  form,  which  will  be  described  in  the  next 
chapter.  The  general  practice  at  even  the  large  mills  seems  to 
be  to  use  several  small  crushers  in  place  of  one  large  one.  The 
rock  usually  falls  from  the  discharge  of  the  crusher  into  the  ele- 
vator buckets  and  is  dropped  from  them  into  a  spout  leading  into 
rotary  dryers,  Fig.  7  A.  These  are  cylindrical  in  shape,  about  4 
feet  in  diameter  and  40  feet  in  length.  They  are  unlined  and  are 
usually  provided  with  angle  irons  bolted  to  the  inside  to  act  as 


7o  PORTLAND  CEMENT 

shelves  (Fig.  7  B)  to  carry  the  rock  up  and  expose  it  to  the  hot 
gases.  Some  of  them  have  their  upper  half  divided  into  four 
compartments  (Fig.  7  C)  by  means  of  plates  in  order  to  expose 
a  greater  surface  of  rock.  They  are  heated  by  a  coal  fire  at  the 
lower  end. 


Fig.  yB.     Rotary  Dryer,  Shelves.  Fig.  7  C.     Rotary  Dryer  Compartments. 

They  are  similar  in  construction  to  the  rotary  kiln  described  in 
Chapter  VII.  One  dryer,  40x4  ft.,  will  take  care  of  about  200 
250  tons  of  rock  in  24  hours 

Wet  Process. 

The  marl  is  usually  received  at  the  mill  whether  it  comes  by 
cars,  barge  or  pipe  line  in  the  form  of  a  thin  mud.  After  remov- 
ing roots,  sticks,  stones,  etc.,  this  slurry  is  stored  in  large  concrete 
basins  or  steel  tanks.  The  clay  is  usually  dried  to  facilitate  the 
chemical  work  of  obtaining  a  proper  mixture,  and  disintegrated 
in  edge  runner  mills  or  dry  pans.  From  the  storage  tank  the 
marl  is  pumped  either  into  a  tank  of  known  volume  or  the  hop- 
per of  a  scale.  The  clay  is  elevated  to  bins  above  this  and  mixed 
as  directed  by  the  chemist.  From  the  measuring  tank  or  scales, 
the  mixture  is  dumped  into  a  "pug"  mill  and  thoroughly  mixed. 
From  the  pug  mill  the  mass  is  run  into  large  vats  where  it  is 
sampled  and  analyzed.  If  of  correct  composition  it  is  passed  on 
for  final  grinding,  if  not,  the  required  quantity  of  marl  or  clay  as 
the  case  may  be,  is  added,/  There  should  be  three  or  more  of  these 


QUARRYING,   EXCAVATING,   ETC.,  OF  RAW   MATERIAL  79 

vats  so  that  one  may  be  filling,  one  analyzed,  and  the  third  emp- 
tied all  at  the  same  time.  These  vats  are  provided  with  stirrers 
so  as  to  keep  the  mass  in  constant  agitation  to  prevent  any  part 
of  it  settling  out  and  also  to  mix  in  thoroughly  any  clay  or  marl 
that  may  be  added  here  to  correct  the  mix.  Compressed  air  is 
also  used  for  agitating  the  contents  of  the  slurry  tanks  in  place 
of  the  revolving  arm  with  paddles. 

Agitators  of  the  propeller  form  are  also  used,  in  which  the  shaft 
is  horizontal  instead  of  vertical  and  about  which  blades  are  fixed. 

As  dredged  from  the  deposit  the  marl  contains  from  40  to  50 
per  cent,  water,  which  is  usually  increased  in  the  pug  mills,  in 
order  to  facilitate  pumping  it  from  one  part  of  the  mill  to  an- 
other, so  that  the  slurry  usually  contains  from  60  to  65  per  cent, 
of  water.  Various  mechanical  means  have  been  proposed  for  ex- 
tracting the  moisture  from  the  slurry.  The  following1  is  a  list  of 
these : 

1.  Hydraulic  filter  presses. 

2.  Perforated  belt  passing  between  rolls  which  press  out  the 
moisture. 

3.  Large  wheels  with  wide  perforated  faces  between  which  the 
material  is  pressed  as  it  passes  through. 

4.  Steel  tank  lined  with  porous  tile  and  air  pressure  applied, 
forcing  the  water  through  tile,  and  tank  is  then  drained. 

It  seems  doubtful,  however,  if  any  of  these  mechanical  means 
will  succeed  because  of  the  fine  state  of  subdivision  in  which  the 
marl  and  clay  exist  in  the  slurry.  At  the  present,  therefore,  the 
only  way  of  getting  rid  of  this  excess  of  water  is  by  evapora- 
tion. At  one  or  two  plants  the  attempt  has  been  made  to  dry  the 
marl  in  dryers  similar  to  those  used  for  dry  materials,  such  as 
cement  rock,  and  to  use  a  dry  process.  The  general  plan,  how- 
ever, now  seems  to  be  to  dry  the  slurry  in  the  upper  part  of  the 
rotary  kiln  during  burning,  making  burning  and  drying  one  oper- 
ation. 

Examples  of  Treatment  of  Raw  Material  Preparatory  to  Fine 

Grinding. 
Below  will  be  found  short  descriptions  of  the  methods  employ  - 

1  Soper,  Cement  and  Engineering  News,  Feb.,  1904. 


8O  PORTLAND  CEMENT 

,/ 

ed  at  some  of  the  more  successful  Portland  cement  mills  for  mix- 
ing and  preparing  the  raw  material  for  the  fine  grinding. 

Dry  Process  Mills. 

VULCANITE:  PORTLAND  CEMENT  Co. — Raw  Materials,  Cement 
Rock  and  Limestone.  Cement  rock  is  quarried,  loaded  on  skips 
by  hand,  conveyed  to  the  mill  by  serial  hoist,  where  it  is  sampled 
and  dumped  in  piles.  The  cement  rock  is  wheeled  on  barrows 
from  the  pile  to  the  crusher  where  the  proper  amount  of  lime- 
stone is  added.  The  mix  is  then  dried  in  rotary  dryers  and  sent 
to  the  mill  for  grinding. 

DEXTER  PORTLAND  CEMENT  Co. — Raw  Materials,  Cement  Rock 
only.  Cement  rock  is  quarried,  loaded  on  side  dump  cars  and 
hauled  to  mill  on  incline  railway.  Mix  is  regulated  by  properly 
distributing  cars  between  portions  of  quarry  where  the  rock  is 
high  and  low  in  lime,  respectively.  Rock  is  crushed  in  a  Gates 
crusher  and  divided,  part  of  crushed  rock  going  to  the  mill  and 
part  into  bins  for  the  night.  Rock  is  dried  in  rotary  dryer  just 
before  going  to  ball  mills.  Bins  are  tapped  below  at  night  and 
crushed  rock  sent  to  mill  on  belt  conveyor. 

NAZARETH  PORTLAND  CEMENT  Co. — Razv  Materials,  Cement 
Rock  and  Clay.  Cement  rock  quarried,  loaded  by  hand  on  skips, 
sent  to  mill  by  aerial  hoist  and  piled.  From  piles  rock  is  hauled 
to  the  crusher  where  clay  is  added  as  determined  by  analysis  of 
the  quarry  drill  holes.  Crushed  mix  is  dried  in  rotary  dryers. 

LAWRENCE  CEMENT  Co. — Raw  Materials,  Cement  Rock  and 
Limestone.  Cement  rock  and  limestone  are  quarried  and  loaded 
on  dump  cars  by  hand.  Both  materials  are  crushed  and  dried 
separately,  elevated  into  hopper-shaped  bins  and  stored  separate- 
ly. Analyses  are  then  made  and  the  contents  of  the  bins  mixed 
in  proper  proportions  and  conveyed  to  the  ball  mills. 

ALSEN'S  AMERICAN  PORTLAND  CEMENT  Co. — Razv  Materials, 
Limestone  and  Clay.  Limestone  is  quarried,  loaded  on  cars  and 
crushed  in  Gates  crushers  located  in  the  quarry.  Crushed  stone 
is  screened  with  a  revolving  screen,  the  coarse  material  being  re- 
turned to  the  crushers.  Fine  material  is  sent  to  mill  on  car.  Clay 
is  passed  through  a  disintegrator,  two  rotary  dryers,  another  dis- 


QUARRYING,  EXCAVATING,  ETC.,  OF  RAW   MATERIAL  8 1 

integrator  and  then  through  a  Ruggles-Coles  dryer,  after  which 
it  is  added  to  limestone  in  proper  proportion.  The  mixture  is 
then  dried  in  rotary  dryers  and  sent  to  the  ball  mills. 

ST.  Louis  PORTLAND  CEMENT  Co. — Raw  Materials,  Limestone 
and  Shale.  The  limestone  is  quarried,  crushed  and  screened  at 
the  quarry,  the  fines  only  being  used  for  cement  and  the  screen- 
ings sold  for  macadam  and  ballast.  The  shale  on  arrival  at  the 
mill,  passes  through  a  disintegrator,  after  which  it  is  dried  in 
rotary  dryers  and  stored  in  bins.  The  fine  limestone  is  dried  in 
rotary  dryers  and  stored  in  bins.  The  two  are  then  mixed  and 
pulverized. 

VIRGINIA  PORTLAND  CEMENT  Co. — Raw  Materials,  Limestone 
and  Shale.  The  limestone  is  crushed  in  the  quarry  by  a  No.  5 
Gates  crusher,  and  carried  to  the  mill  by  cars,  here  it  is  dried  in  a 
Ruggles-Coles  dryer,  ground  in  ball  mills  and  stored  in  a  large 
bin.  The  shale  is  dried,  passed  through  a  set  of  Buchanan  rolls 
and  then  ground  in  rock  emery  mills.  The  shale  is  then  stored  in 
a  set  of  five  bins  and  from  these  passes  to  a  bin  beside  the  lime- 
stone bin.  The  two  materials  are  then  mixed  in  proper  propor- 
tions and  ground  in  tube  mills. 

HUDSON  PORTLAND  CEMENT  Co. — Raw  Materials,  Limestone 
and  Shale.  The  cars  from  both  the  limestone  quarry  and  the 
shale  pits  are  dumped  on  the  crusher  house  floor  and  wheeled  to 
the  crushers,  two  of  which  are  used  for  limestone  and  one  for 
shale.  The  two  materials  are  crushed  separately,  dried  in  rotary 
dryers  and  ground  in  ball  mills.  After  which  they  are  stored  in 
bins,  two  of  which  are  for  shale  and  five  for  limestone.  The  two 
materials  are  then  mixed  in  proper  proportions  in  an  automatic 
weighing  machine  and  the  mixture  ground  in  tube  mills. 

ALPHA  PORTLAND  CEMENT  Co. — Raw  Materials,  Cement  Rock 
and  Limestone.  The  cement  rock  is  quarried  and  hauled  up  an 
incline  to  the  mill  where  the  proper  amount  of  limestone,  as  de- 
termined by  analysis  of  the  quarry  drill  holes,  is  added.  The  mix- 
ture is  then  crushed  in  a  Gates  crusher,  dried  in  rotary  dryers,  and 
finely  ground  in  Griffin  mills. 


82  PORTLAND  CEMENT 

Wet  Process  Mills. 

EGYPTIAN  PORTLAND  CEMENT  Co. — Raw  Materials,  Marl  and 
Clay.  Marl  is  dug  up  by  a  dipper  dredge  and  dumped  into  a 
stone  separator  on  a  scow  lashed  to  the  dredge,  from  the  separator 
it  is  transferred  to  barges,  which  convey  it  to  the  shore,  where 
they  are  unloaded  and  the  marl  pumped  to  the  mill  by  a  ball-valve 
Bonnot  slurry  pump.  At  the  mill  the  marl  is  received  in  two 
large  tanks  which  discharge  into  a  pug  mill.  The  clay  is  unloaded 
on  the  floor  of  the  clay  house  and  ground  in  a  dry  pan,  after 
which  it  is  screened  and  elevated  to  a  bin  close  to  the  marl  bin. 
The  marl  and  clay  are  then  mixed  in  the  pug  mill  in  proper  pro- 
portions, passed  into  a  storage  tank,  ground  in  emery  mills,  and 
then  spouted  to  either  of  two  shallow  pits,  where  it  is  held  for 
analysis  and  corrected  if  necessary.  The  slurry  is  then  pumped 
through  the  tube  mills  for  the  final  grinding. 

BRONSON  PORTLAND  CEMENT  Co. — Raiv  Materials,  Marl  and 
Clay.  Marl  is  excavated  by  a  dipper  dredge  mounted  on  a  scow, 
which  floats  in  the  channel  cut  by  the  dipper.  The  marl  is  carried 
to  the  mill  by  cars,  which  dump  into  pug  mills  made  to  act  also  as 
stone  separators.  From  these  the  marl  is  spouted  into  concrete 
storage  tanks,  where  it  is  analyzed  and  pumped  to  the  mixing 
floor.  The  clay  is  ground  in  edge  runner  mills  (or  dry  pans)  and 
from  these  elevated  to  a  bin  above  the  mixing  floor,  where  it  is 
added  to  the  marl,  in  the  amount  determined  by  analysis;  after 
which  the  mixture  is  thoroughly  pugged,  the  pug  mills  discharg- 
ing by  gravity  into  tube  mills  where  the  final  grinding  takes  place. 

OMEGA  PORTLAND  CEMENT  Co. — Marl  and  Clay.  Marl  is 
dredged,  the  dipper  dropping  it  into  buckets  on  cars,  each  car 
carrying  two  buckets  and  each  bucket  of  one  cubic  yard  capacity. 
The  cars  are  hauled  to  a  trestle  or  trolley,  which  picks  up  the 
buckets  and  carries  them  into  the  wet  mill,  where  they  are  dis- 
charged into  a  stone  separator.  From  the  stone  separator  the 
marl  passes  into  vats  where,  after  thorough  agitation,  it  is  sam- 
pled and  analyzed.  It  is  then  pumped  into  three-yard  measuring 
cylinders,  the  proper  amount  of  clay  addeed  to  it,  and  the  mixture 
passed  through  a  pug  mill  to  the  tube  mills  for  final  grinding. 

NEWAGO  PORTLAND  CEMENT  Co. — Raiv  Materials,  Marl  and 


QUARRYING,  EXCAVATING,  ETC.,  OF  RAW   MATERIAL  83 

Clay.  The  marl  is  dredged  and  lifted  to  5O-ton  cars,  which  dump 
it  into  a  bin  (or  a  storage  place  under  a  trestle  for  use  in  winter). 
From  the  bin  the  marl  flows  through  a  bottom  valve  into  a  stone 
separator  and  enough  water  is  added  to  make  the  slurry  man- 
ageable with  a  pump.  From  the  separator  it  passes  to  three  90- 
cubic-yard  storage  bins  where  it  is  analyzed.  It  is  then  pumped 
to  measuring  tanks  where  the  clay  is  added.  The  clay  after  being 
received  at  the  mill  is  dried,  passed  through  rolls  and  into  a  pug 
mill  where  water  is  added.  On  passing  out  of  this,  it  is  ground 
between  buhr  stones  and  pumped  to  the  measuring  tank  to  be 
added  to  the  marl.  From  the  measuring  tanks  the  mixture  is  fed 
to  a  measuring  hopper  and  thence  to  three  po-cubic-yard  tanks 
where  it  is  analyzed  and  corrected  if  necessary.  From  these  vats 
the  slurry  passes  to  the  tube  mills,  where  it  is  finely  ground  for 
burning. 


CHAPTER  VI. 


GRINDING  THE  RAW  MATERIAL  AND  GRINDING 
MACHINERY. 

In  the  early  days  of  the  industry  when  the  plants  were  small, 
manufacturing  only  a  few  thousand  barrels  a  year  each,  both  the 
raw  rock  and  the  clinker  were  ground  with  mill  stones,  just  as 
natural  cement  is  now,  and  just  as  corn  is  ground  in  the  small 
water  power  mills  familiar  to  every  one.  The  first  advance  upon 
this  was  to  encase  the  stones,  and  as  the  mills  began  to  work  up 
a  home  market  for  their  product  and  to  increase  their  output  to 
meet  this  demand,  they  also  began  to  experiment  with  various 
forms  of  fine  grinders.  As  a  result  of  their  experiments  the  Atlas 
Portland  Cement  Co.  patented  the  Huntingdon  mill  which  they 
still  use.*  In  1889  the  American  Cement  Co.  installed  a  Griffin 
mill  in  their  plant  at  Egypt  and  this  mill  is  still  in  use  there,  and 
in  many  other  large  mills  throughout  the  country.  Another  sys- 
tem of  grinding  consisting  of  a  ball  mill  for  the  coarse  grinding 
and  a  tube  mill  for  the  final  pulverization  was  introduced  about 
this  time  by  the  Bonneville  Cement  Co.  in  their  plant  at  Sieg- 
fried, Pa.,  and  this  combination  also  has  come  into  prominent  use 
in  the  industry.  Recently  the  Kent  mill  has  been  introduced  in 
several  Portland  cement  plants,  and  its  users  report  favorably 
upon  it. 

Edison  in  his  new  mammoth  plant  at  Stewartsville,  N.  J.,  has 
installed  a  system  of  grinding  by  rolls.  The  rock  passes  in  a  solid 
stream  through  the  rolls,  undergoing  considerable  compression  as 
it  does  so.  The  crushed  material  is  then  dropped  in  front  of  re- 
volving fans  which  blow  out  the  fine  particles  into  large  settling 
chambers.  The  coarse  material  is  then  returned  to  the  rolls,  etc. 

Crushers. 

In  the  use  of  any  of  the  above  mills  upon  dry  raw  materials  it 
is  necessary  to  break  up  the  material  to  a  size  of  about  2-3  inches 
in  diameter.  In  order  to  do  this,  as  has  been  stated,  crushers  of 


GRINDING  RAW   MATERIAL  AND   MACHINERY  85 

the  Gates  gyratory  type  are  usually  employed.  This  crusher  was 
developed  by  the  Gates  Iron  Works,  Chicago,  but  is  now  made 
and  sold  by  several  firms.  The  jaw  or  Blake  crusher  is  also  used 
to  some  extent,  though  nothing  like  so  generally  as  the  gyratory 
type.  The  Gates  crusher  is  sometimes  followed  by  a  coffee-mill 
crusher,  particularly  where  Griffin  mills  are  used  for  fine  grind- 
ing. This  coffee-mill  crusher  is  described  in  the  section  on  pul- 
verizing coal  in  Chapter  VII.  The  Williams  mill  also  used  after 
the  Gates  crusher  and  before  the  tube  mill  or  Griffin  mill  is  also 
described  there. 

Below  will  be  found  descriptions  of  the  Griffin,  three-roll  Grif- 
fin, Huntington,  ball  and  tube  mills,  and  the  Kominuter,  and  on 
page  98  will  be  found  a  table  showing  the  capacity  of  these  mills 
and  the  power  required  to  run  them. 

Gates  Crusher. 

Fig.  8  shows  a  section  of  a  Gates  crusher.  Referring  to  this 
illustration,  on  the  spindle  gt  is  mounted  the  chilled-iron  crushing 
head  c.  The  hopper-shaped  top  shell  h  is  lined  with  concave  chill- 
ed plates.  The  crushing  is  done  in  the  annular  space  between  the 
chilled  surfaces. 

The  spindle  being  centrally  held  in  the  spider  at  the  top  rests 
at  its  lower  end,  passing  loosely  through  an  eccentric  driven  by 
bevels  b.  The  spindle  thus  receives  a  gyrating  motion  and  may 
or  may  not  rotate.  Thus,  one  point  in  the  annular  space  is  wide, 
while  a  point  opposite  is  narrow,  and  the  crushing  force  is  ob- 
tained on  account  of  the  head  approaching  and  receding  from  the 
concaves.  In  the  type  described  the  largest  motion  is  at  the  bot- 
tom where  the  annular  space  is  narrow,  and  this  motion  is  the 
throw  or  stroke.  The  number  of  revolutions  of  the  spindle  and 
number  of  strokes  correspond,  generally  being  about  200  per 
minute.  On  a  crusher  having  an  annular  opening  at  the  top,  10 
in.  X  60  in.  circumference,  the  stroke  would  generally  be  about 
y%  inch.  These  machines  work  continuously  and  for  this  reason 
are  steady  in  the  power  required. 

As  far  as  oscillating  motion  goes  they  are  not  balanced  and 
therefore  give  rise  to  vibration  if  not  on  good  foundation. 


86 


PORTLAND  CEMENT 


They  are  used  for  the  very  largest  capacity.  They  are  well 
adapted  for  careless  feeding  or  feeding  directly  from  cars,  and 
the  rock  can  be  fed  from  all  directions. 

The  machines  are  massive  and  repairs  generally  require  hand- 
ling large  parts.  On  account  of  the  sidewise  rolling  of  the  head 
upon  the  ''concaves"  this  crusher  is  less  liable  to  choke  than  the 
ordinary  jaw  crusher. 


Fig.  8.     Gates  Crusher. 

The  power  required  to  operate  this  crusher  upon  rocks  of  mod- 
erate hardness  is  from  i  to  1.2  H.  P.  per  ton  of  rock  crushed  per 
hour. 

Blake  Crusher. 

The  Blake  crusher  is  shown  in  Fig.  9.   It  consists  of  the  follow- 


GRINDING  RAW   MATERIAL  AND   MACHINERY  87 

ing  parts :  /,  the  frame ;  kt  zinc  backing ;  c,  still  plate  or  stationary 
plate;  c,  movable  jaw  plate;  d,  jutman;  b,  swing  jaw  or  mov- 
able jaw;  et  toggle  bearings  or  seats;  p,  toggles;  t,  front  or 
toggle  block;  w,  back  or  wedge  block;  side  liners  or  checks,  one 
at  each  side  of  mouth ;  g,  shaft  and  eccentric ;  h,  bar  or  swing  jaw 
shaft. 

The  eccentric  shaft  pulls  up  the  pitman,  straightens  out  the  tog- 
gles and  this  moves  the  swing  jaw  while  crushing.  The  angle 
between  the  plates  requires  to  be  small  enough  to  nip  the  rock, 
but  large  enough  to  give  capacity  or  a  large  mouth  without  ex- 
cessively long  plates.  The  movement  at  the  bottom  or  throat  is 
the  stroke.  The  number  of  effective  strokes  is  the  same  as  the 
number  of  revolutions  of  the  pulley,  since  no  crushing  is  done  on 
the  return  stroke;  the  rod  m  pulls  the  swing  jaw  back  against  the 
toggles  during  the  return  stroke.  Half  the  time  is  occupied, 
therefore,  in  storing  up  energy  in  the  flywheels. 


Fig.  9      Blake  Crusher. 

The  Griffin  Mill. 

The  Griffin  mill  is  shown  in  Fig.  10.  Referring  to  this  it  will 
be  seen  that  the  power  is  received  by  a  pulley  (17)  running  hori- 
zontally. From  this  pulley  is  suspended  the  shaft  (i)  by  means 
of  a  universal  joint  (9)  and  to  the  lower  extremity  of  this  shaft 


88  PORTLAND  CEMENT 

is  rigidly  secured  the  crushing  roll  (31),  which  is  thus  free  to 
swing  in  any  direction  within  the  case. 

A  reference  to  the  illustration  on  the  opposite  page  will  show 
that  this  case  consists  of  the  base,  or  pan  (24),  containing  the 
ring,  or  die  (70),  against  which  the  roll  (31)  works,  and  upon 
the  inner  vertical  surface  of  which  the  pulverizing  is  done. 

In  dry  pulverizing  this  pan,  or  base  (24),  has  a  number  of 
openings  through  it  downward,  outside  of  the  ring,  or  die,  which 
lead  into  a  pit,  or  receptacle,  from  which  it  is  delivered  by  a  con- 
veyor. 

Upon  this  base  is  secured  the  screen  frame  (44),  which  is  sur- 
rounded with  a  sheet-iron  cover  (45),  (in  the  wet  mill  this  cover 
is  not  used),  and  to  the  top  of  which  is  fastened  a  conical  shield 
(25),  open  at  the  apex,  through  which  the  shaft  works. 

The  cut  on  page  90  shows  the  pulverizing  roll  attached  to  the 
lower  end  of  the  shaft  (i),  and  just  above  the  roll  is  the  fan  (7), 
which  is  used  in  the  dry  mill,  but  not  in  the  wet.  On  the  under 
side  of  the  roll  are  shown  shoes,  or  plows  (5),  which  are  used  in 
both,  and  varied  in  shape  according  to  the  nature  of  the  work  to 
be  done. 

The  pulley  (17)  revolves  upon  the  tapered  and  adjustable  bear- 
ing (20),  which  is  supported  by  the  frame  composed  of  the  stand- 
ards (23).  Two  of  these  standards  (23a)  are  extended  above 
the  pulley  to  carry  the  arms  (22),  in  which  is  secured  the  hollow 
journal  pin  (12). 

Within  the  pulley  is  the  universal  joint  from  which  the  shaft 
(i)  is  suspended.  This  joint  is  composed  of  the  ball,  or  sphere 
(9),  with  trunnions  attached  thereto.  These  trunnions  work  in 
half  boxes  (u)  which  slide  up  and  down  recesses  in  the  pulley- 
head  casting  (16). 

The  joint  in  the  pulley  is  enclosed  by  means  of  the  cover  (13), 
thus  keeping  the  working  parts  away  from  all  dust  and  grit. 

The  lubricating  oil  is  supplied  for  all  parts  needing  it  through 
the  hollow  pin  (12). 

The  roll  is  revolved  within  the  die  in  the  same  direction  that 
the  shaft  is  driven,  but  when  coming  in  contact  with  the  die  it 


GRINDING  RAW   MATERIAL  AND   MACHINERY  89 

travels  around  the  die  in  the  opposite  direction  from  that  in  which 
the  roll  is  revolving  with  the  shaft,  thus  giving  the  mill  two  di- 
rect actions  on  the  material  to  be  ground.  There  is  a  pressure 
by  centrifugal  force  of  6,000  pounds  brought  to  bear  on  the  mate- 
rial being  pulverized  between  the  roll  and  die,  the  united  actions 
being  very  effective  in  their  combination. 

When  a  quantity  of  the  material  to  be  reduced  has  been  fed 
into  the  mill,  sufficient  to  fill  the  pan  as  high  as  the  shoes,  or 
plows,  on  the  lower  side  of  the  roll,  they  work  in  it,  stir  it  up, 
and  throw  it  against  the  ring,  so  that  it  is  acted  upon  by  the  roll ; 
and  when  fairly  in  operation  the  whole  body  of  loose  material 
whirls  around  rapidly  within  the  pan,  and,  being  brought  between 
the  roll  and  die,  is  crushed,  and  all  that  is  sufficiently  fine  passes 
at  once  through  the  screen  above  the  die,  the  coarser  portion  fall- 
ing down  to  be  acted  upon  again. 

The  universal  joint,  by  which  the  shaft  is  connected  with  the 
pulley,  allows  perfect  freedom  of  movement  to  the  roll,  so  that  it 
can  safely  pass  over  pieces  of  iron,  steel,  etc.,  such  as  are  usually 
found  in  all  material  to  be  pulverized,  without  damage  to  the 
mill. 

The  fan  attached  to  the  shaft  above  the  roll  draws  air  in  at  the 
top  of  the  cone,  forcing  it  through  the  screens  and  out  into  the 
discharge,  thus  effectually  keeping  all  dust  within  the  mill. 

In  working  dry  the  screen  which  surrounds  the  pulverizing 
chamber  is  of  much  coarser  mesh  than  the  delivered  product ;  for 
instance,  a  16  mesh  screen  delivers  a  product  over  90  per  cent,  of 
which  will  pass  a  loo-mesh  screen.  There  is,  in  consequence,  no 
clogging  by  reason  of  having  to  use  fine  mesh  screens  in  order  to 
secure  fine  products. 

A  Griffin  mill  of  the  size  usually  installed  in  Portland  cement 
mills  will  grind  from  iy2  to  3  tons  of  rock  per  hour,  the  amount 
varying  with  the  hardness  of  the  rock  and  the  condition  in  which 
the  mill  is  kept.  In  doing  this  work  it  will  consume  from  25  to 
28  horse  power.  The  cost  of  keeping  these  mills  in  repairs  is 
from  i  to  \y2  cents  per  barrel  ground. 

Three  Roll  Griffin  Mill 
This  is  a  new  mill  recently  brought  out  by  the  manufacturers 


PORTLAND  CEMENT 


of  the  Griffin  mill,  which  is  somewhat  similar  in  principle  to  the 
single  roll  Griffin  mill.  It  is  shown  in  Fig.  n,  and  as  its  name 
implies  it  has  three  rolls  in  place  of  one.  It  is  provided  with 


Fig.  10.    The  Griffin  Mill. 

screens,  fans  and  ploughs  which  perform  the  same  work  as  in  the 
old  style  Griffin  mill.  These  mills  have  been  given  a  thorough 
trial  on  grinding  raw  material,  but  so  far  have  been  only  used 


Fig.  n.     Three  Roll  Griffii 


GRINDING  RAW   MATERIAL  AND   MACHINERY  QI 

experimentally  for  grinding  clinker.  One  of  the  newer  mills  in 
the  Lehigh  District  has  its  entire  raw  side  equipped  with  these 
mills  and  reports  .from  this  plant  credit  them  with  doing  remark- 
ably well.  The  three  roll  mill  requires  4O-horse-power  to  run  and 
will  grind  5  to  6  tons  of  cement  rock-  limestone  mixture  per  hour 
to  a  fineness  of  96%  through  a  loo-mesh  screen.  The  new  mill 
is  said  to  be  not  only  more  efficient  than  the  single  roll  Griffin 
mill,  but  to  also  require  less  repairs,  and  consequently  to  cost  less 
to  keep  in  order. 

Huntington  Mill. 

The  Huntington  mill  is  another  mill  of  the  impact  or  percus- 
sion type  and  is  somewhat  similar  to  the  former  in  construction, 
so  far  as  the  writer  knows  it  is  used  only  by  the  Atlas  Portland 
Cement  Co.,  Northampton,  Pa. 

The  Huntington  mill,  Fig.  12,  has  shells  freely  suspended  on 


Fig   12.     Huntington  Mill. 

spindles  from  a  revolving  spider.  The  revolution  causes  the 
shells  to  swing  out  and  crush  against  the  edge  of  the  die  ring. 
The  machine  generally  is  a  great  consumer  of  repairs. 


Q2  PORTLAND  CEMENT 

The  Ball  Mill 

The  ball  mill  is  of  European  origin  and  was  used  for  grinding 
Portland  cement  in  Germany  before  its  introduction  into  this 
country.  It  is  usually  used  in  connection  with  the  tube  mill  to 
prepare  the  material  for  the  latter,  the  ball  mill  reducing  it  to  a 
coarse  grit  and  the  tube  mill  completing  the  operation. 


Fig.  13.     Ball  Mill,  Section  Showing  Grinding  Plates  and  Sieves. 

Figs.  13  and  14  show  the  construction  of  a  ball  mill.  It  consists 
of  a  drum  filled  with  steel  balls.  The  drum  is  lined  first  with 
steel  plates,  (d)  which  lap  one  over  the  other  to  form  steps.  As  the 


GRINDING  RAW   MATERIAL  AND   MACHINERY 


93 


drum  revolves,  the  balls  drop  over  the  steps  pounding  the  mate- 
rial to  pieces.  The  partially  ground  material  then  drops  through 
holes  in  the  plates  on  to  perforated  steel  screens  (g)  bolted  around 


Fig.  14.      Ball  Mill,  Section  through  the  Shaft. 

the  entire  circumference  of  the  drum.  These  screens  take  out  the 
very  coarse  particles  and  return  them  to  the  inside  of  the  drum. 
The  finer  ones  drop  on  another  set  of  screens  (I)  made  of  woven 
wire  cloth,  and  these  separate  the  fully  ground  material  from  the 
coarse  and  return  the  latter  back  to  the  mill. 


94  PORTLAND  CEMENT 

The  fully  ground  material  falls  into  the  dust  proof  casing, 
which  entirely  surrounds  the  mill,  and  then  down  to  the  conveyor 
running  underneath  the  latter. 

The  ends  of  the  drum  are  formed  by  circular  plates.  In  the 
Gates  and  Krupp  forms  of  this  mill  and  also  in  the  smaller  size 
of  the  Smidth  mill  these  plates  have  rigidly  attached  to  their  cen- 
tres, hubs  which  are  mounted  on  to  a  heavy  shaft  which  revolves 
in  dust-proof  bearings.  One  of  the  hubs  is  provided  with  open- 
ings through  which  the  material  to  be  ground  is  fed.  In  the 
large  size  Smidth  mills  the  shaft  is  omitted  and  the  hub  rests  on 
roller  bearings  giving  a  full  circular  opening  which  will  admit  of 
the  passage  of  lumps  10  inches  in  diameter  into  the  mill.  The 
feeding  device  of  the  Smidth  mills  consists  of  a  circular  revolving 
table  provided  with  a  scraper.  The  material  to  be  ground  is 
brought  down  upon  the  table  by  a  spout  which  stops  short  a  few 
inches  from  the  former.  As  the  table  revolves  the  material  flows 
out  of  the  spout  upon  it  and  as  it  comes  around  to  the  scraper  is 
brushed  off  into  the  hopper  of  the  mill.  The  feed  can  be  regulated 
by  adjusting  the  scraper  so  as  to  brush  off  a  greater  surface  of  the 
table.  The  Gates  ball  mill  has  a  swinging  feeder. 

The  size  of  the  product  of  the  ball  mill  is  regulated  entirely  by 
the  fineness  of  the  finishing  screens.  Those  on  mills  intended  to 
grind  raw  material  are  usually  16  to  18  mesh  and  those  on  mills 
for  clinker  from  18-20  mesh.  It  is  generally  economy  to  so  bal- 
ance the  screens  as  to  get  the  most  out  of  the  tube-mill,  however, 
since  the  ball  mill  requires  much  less  power  than  the  tube-mill 
and  consequently  up  to  a  certain  point  should  be  made  to  do  all 
the  work  it  will.  The  screens  of  the  ball -mill  are  apt  to  leak  occa- 
sionally, both  from  wear  and  also  from  the  dropping  out  of  a 
rivet  or  bolt.  A  good  check  upon  this  is  to  run  sieve  tests  of  the 
product  upon  a  No.  20  sieve  once  or  twice  a  day  and  any  abnor- 
mal weight  of  residue  should  be  followed  by  an  examination  of 
the  screens  for  leaks.  It  is  necessary  to  brush  the  screens  off 
occasionally  with  a  wire  brush  as  they  clog  with  use. 

A  ball  mill  usually  requires  from  30  to  40  horse  power  and 
turns  out  from  4  to  6  tons  of  raw  material  per  hour.  The  balls 
run  in  sizes  from  3  to  5  inches  in  diameter  and  the  charge  of  balls 
for  a  mill  of  the  above  size  weighs  usually  about  a  ton  and  a  half. 


GRINDING  RAW   MATERIAL  AND   MACHINERY 


95 


The  Kominuter. 

A  modification  of  the  ball  mill  which  has  been  introduced  in  the 
last  three  years  by  Messrs.  F.  L.  Smidth  &  Co.  is  the  Kominuter. 
This  form  of  mill  is  intended  to  do  the  work  of  the  ball  mill  and 
has  about  double  the  capacity  of  the  latter.  It  consists,  Fig.  15, 


Fig.  15.     The  Kominuter. 

of  a  drum  of  about  the  same  diameter  as  a  ball  mill  but  of  about 
twice  the  length  of  the  latter,  suspended  on  a  shaft  supported  by 
bearings.  The  kominuter  is  lined  just  as  a  ball  mill  is  with 
wrought  iron  or  steel  grinding  plates  arranged  to  lap  and  form 
steps.  The  drum  is  surrounded  by  a  coarse  screen  tilting  slightly 
towards  the  feed  end,  and  outside  of  this  screen,  yet  another  one 
of  wire  cloth.  The  material  enters  through  an  opening  beside  the 
shaft  and  is  pounded  to  pieces  by  the  balls.  It  does  not  fall  out 
through  the  screens,  however,  at  once,  but  travels  through  the  full 
length  of  the  drum  and  passes  through  openings  at  the  opposite 
end,  on  to  the  first  coarse  screen,  or  perforated  plate.  The  parti- 
cles too  large  to  pass  through  this  are  returned  automatically  to 
the  interior  of  the  mill  by  means  of  buckets  and  S  shaped  pipes. 
The  material  passing  the  inside  screen  is  caught  upon  the  outside 
one  of  wire  cloth  and  separated  further  here,  the  coarse  material 
being  returned  to  the  mill  as  before. 

The  Tube  Mill. 
The  tube  mill,  Fig.  16,  consists  of  a  cylinder,  20  to  22  feet  long, 


96  PORTLAND  CEMENT 

and  from  60  to  66  inches  in  diameter,  filled  with  flint  balls.  This 
cylinder  is  lined  with  some  hard  substance  such  as  armor  plate, 
chilled  steel,  quartz,  or  trap-rock  and  revolves  at  a  speed  of  from 


Fig.  16.     Smidth  Tube  Mill. 

25  to  27  revolutions  per  minute.  The  material  is  fed  in  through  a 
hollow  shaft  and  leaves  either  in  the  same  manner  at  the  opposite 
end  or  else  through  a  grating  at  the  perimeter  of  the  end.  In  the 
Smidth  tube  mill  the  latter  course  is  pursued,  and  in  the  Gates 
and  Krupp  mills  the  former  plan  is  followed.  The  Krupp  mill  is 
also  divided  into  compartments  forcing  the  material  to  travel  in 
a  zig-zag  motion  through  the  mill.  The  other  two  types  are  with- 
out compartments.  The  flint  pebbles  are  generally  imported  from 
Europe  and  wear  at  the  rate  of  about  one  pound  to  thirty  barrels 
of  cement.  Steel  balls  are  sometimes  used  in  tube  mills  grinding 
wet  materials.  The  material  is  usually  fed  into  the  tube  mill  by 
means  of  a  screw  conveyor  operated  by  a  step-pulley  which  per- 
mits the  cutting  down  of  the  feed,  or  by  a  roller  feed  with  mov- 
able gate,  or  by  a  shaker  feed,  any  of  which  can  be  adjusted  to 
regulate  the  amount  of  material  going  into  the  mill.  A  tube  mill, 
51/2x20  feet,  -usually  requires  80  horse-power  to  run  and  about 
double  that  quantity  momentarily  in  starting.  It  should  turn  out 
about  12  to  1 6  barrels  of  clinker  per  hour 

In  the  dry  process  it  is  usual  to  grind  both  the  raw  material  and 
the  clinker  in  the  same  type  of  grinder,  though  at  some  mills  the 
raw  materials  are  ground  in  ball  and  tube  mills  and  the  clinker  in 
Griffin  mills.  In  the  wet  process  the  tube  mill  is  nearly  always 
used  to  reduce  the  slurry  to  the  necessary  fineness,  but  either  ball 
and  tube  or  Griffin  mills  can  grind  the  clinker.  It  is  necessary 


GRINDING  RAW   MATERIAL  AND   MACHINERY  97 

usually  to  break  up  the  rock  with  rolls  or  some  other  form  of 
crusher  before  feeding  it  to  Griffin  mills.  The  proposition  has 
been  made  to  do  this  preparatory  work  with  kominuters.  When 
the  wet  process  is  used  it  is  usual  to  break  up  the  clay  with  an 
edge  runner  mill  or  dry  pan  which  also  serves  as  a  mixer. 

It  consists  of  a  cast  iron  pan,  in  which  heavy  iron  rollers  re- 
volve, the  clay  being  crushed  between  the  bottom  of  the  pan  and 
the  rollers. 

Capacity  of  Various  Grinders. 

Below  will  be  found  a  table  (XVII)  giving  the  capacity  of  the 
various  machines  used  for  crushing  and  grinding  the  raw  mate- 
rials and  clinker  in  a  cement  mill.  It  is  compiled  from  results  ob- 
tained in  actual  practice  and  the  output  of  the  various  machines  is 
the  average  for  long  periods  of  time  and  includes  shut-down  for 
ordinary  repairs,  etc.  For  instance,  when  the  capacity  of  a  No.  6 
Gates  crusher  is  given  as  30  to  40  tons  per  hour  it  means  that  this 
size  crusher  will  crush  300  tons  day  in  and  day  out  of  ten  hours, 
and  not  just  30  tons  for  a  test  run  of  an  hour.  Similarly  when 
the  capacity  of  a  No.  7  ball  mill  is  given  at  12  barrels  an  hour  it 
means  that  three  of  them  will  safely  take  care  of  the  clinker  end 
of  a  four-kiln  dry  process  plant,  allowing  for  shut-downs  to  clean 
and  renew  screens,  put  in  new  plates,  etc.  In  each  case  the  lower 
figure  in  the  table  is  the  safe  one  to  assume  as  the  least  capacity 
of  the  mill  in  question  when  properly  handled.  The  fineness  of 
the  output  is  an  important  item  in  determining  the  output  of  a 
mill.  In  one  instance  which  the  writer  recently  observed,  a  tube 
mill  ground  cement  on  an  average  12  barrels  an  hour  to  a  fineness 
of  97%  through  a  No.  100  sieve,  and  on  increasing  the  feed  15 
barrels  an  hour  to  a  fineness  of  92%  passing  a  No.  200  sieve,  or  an 
increase  of  3  barrels  an  hour,  or  25%  more  for  a  decrease  of  5% 
in  fineness.  In  making  comparisons  between  two  forms  of  grind- 
ers, therefore,  it  is  necessary  that  the  fineness  of  the  product  pro- 
duced by  each  should  be  the  same,  not  only  when  tested  by  the 
No.  100  sieve  but  also  by  the  No.  200,  as  a  difference  of  2%  in 
fineness  may  easily  represent  a  difference  of  10%  in  output. 

4 


PORTLAND  CEMENT 


TABLE  XVII.— GIVING  CAPACITY,  ETC.,  OF  CRUSHERS  AND  MILLS 
USED  IN  GRINDING  RAW  MATERIALS  AND  CLINKER. 


Output  p 

er  Hour. 

Type  of  Mill. 

Size. 

£  Charge  of 
§>  Balls. 

M  Horse-powe 
Required  to 
^d  Operate.1 

I! 
«I 

Tons. 

h 

• 

o 

Tons. 

tJ 

n 
a 

*n  ?*> 

Ctf^ 

So 

0 

Tons. 

g| 

o 
Barrels. 

riofpc  Civra 

No   5  D 

No  6  D 

^0    uu  OO 

No   7 

•7   to    C 

4  to  6 

12  to  1  6 

Ball  Mill.3 

No   8 

4^OO 

40  to  50 

A  to  7 

r  to  8 

18  to  25 

r  'x22' 

7O  to  80 

•5  to  A 

4  to  6 

8  to  12 

I  2  to   1  6 

Tube  Mill.4 

r'6'/x2o' 

80  to  QO 

4  to  6 

c  to  8 

jo  to  i  ^ 

1  6  to  20 

Griffin  Mill  5 

•7<y/ 

23  to  28 

I-1  to  2 

2  to  "* 

5  to  8 

Three  Roll 

0^ 

/i  to  6 

Griffin  Mill.5 

No  66 

66OO 

4U 

6  to  8 

7O  to  1^ 

K>nr  Mill  6 

IU   / 

o^  LW  oo 
JO  to  12 

*O  uu  oo 

Degree  of  Fineness. 

The  degree  of  fineness  to  which  the  raw  material  should  be 
ground  depends  largely  upon  conditions.  It  may  be  said  as  a 
general  rule  that  it  should  never  be  ground  coarser  than  90  per 
cent,  through  a  loo-mesh  sieve  and  that  in  most  cases  95  to  98 
per  cent,  is  required  to  produce  a  sound  cement.  Fine  grinding 
will  also  lessen  the  quantity  of  coal  required  for  burning  because 
the  more  intimate  mixture  of  the  lime  with  the  silica  and  the 
alumina  promotes  a  more  rapid  combination  of  these  elements,  as 
sintering  only  takes  place  between  surfaces,  and  the  more 
minute  the  particles  are,  the  greater  surface  will  be  exposed.  For 
a  similar  reason  if  the  raw  material  is  too  coarsely  ground  the 
lime  can  not  get  at  the  silica  and  alumina  to  combine  with  them. 
The  fineness  of  the  raw  material  should  be  tested  at  least  once  a 

1  About  double  this  power  is  required  momentarily  in  starting  the  mills. 

2  Product  passing  a  i  inch  screen. 

3  Fed  with  product  of  crusher  or  clinker  as  it  comes  from  coolers  and  provided  with 
i6-mesh  screens  of  No.  23  wire. 

*  Fed  with  product  of  ball  mills.     Finished  material  95$  through  a  No.  100  sieve. 

6  Fed  with  clinker  or  rock  crushed  to  one-half  inch.  Finished  material  95$  through 
a  No.  100  sieve. 

6  Fed  with  clinker  from  coolers  and  finished  product  to  be  95$  through  a  No.  100  test 
sieve. 


GRINDING  RAW   MATERIAL  AND   MACHINERY  99 

day  and,  if  possible,  two  or  three  times  a  day  in  order  to  have  a 
check  upon  the  work  of  the  mills  and  to  keep  them  up  to  stand- 
ard. The  raw  material  can  be  tested  on  the  loo-mesh  sieve 
by  the  method  for  fineness  outlined  in  the  chapter  on  "Physical 
Testing." 

Conveyors. 

The  material  is  usually  conveyed  from  one  part  of  the  mill  to 
another  by  mechanical  means.  The  product  of  the  Gates  crusher 
is  carried  to  the  ball  mill  bins  or  the  rolls  on  belt  conveyors  or 
scraper  conveyors,  and  the  fine  material  from  the  ball  mills  and 
the  tube  mills  is  conveyed  by  means  of  screw  conveyors.  The 
elevating  is  done  by  bucket  elevators  of  the  link  belt  form.  Slur- 
ry and  marl  are  pumped,  using  either  the  compressed  air  system 
mentioned  before  or  a  plunger  pump  of  special  design  for  the 
work.  Dry  material  is  stored  in  steel  bins  at  every  stage  of  the 
process  in  order  to  have  a  constant  supply  for  each  unit  of  the 
grinding  system,  and  marl  and  slurry  are  stored  in  concrete  vats 
or  steel  tanks  and  kept  in  constant  motion  to  prevent  the  heavier 
and  sandy  portions  from  settling  out. 


CHAPTER  VIL 


KILNS  AND  BURNING, 


Shaft  Kiln. 

The  first  Portland  cement  made  both  in  Europe  and  America 
was  burned  in  upright  or  dome  kilns,  in  which  the  raw  material 
is  moulded  into  bricks  and  charged  alternately  with  layers  of  coke. 
The  kiln  is  unloaded  at  the  bottom  and,  after  the  clinker  is 
drawn,  it  is  carefully  gone  over  by  men  or  boys  and  the  over 
burned  and  underburned  sorted  out  and  rejected.  The  prop- 
erly burned  clinker  only  is  ground.  These  kilns  are  similar 
to  those  used  for  burning  lime,  and  their  form  is  shown 
in  Fig.  17.  From  their  shape  they  are  also  called  "bot- 


Fig.  17.     Dome  Kiln. 

tie"  kilns.  They  are  intermittent  in  action,  that  is  they 
must  be  freshly  charged  for  each  burning.  On  this  ac- 
count there  is  considerable  loss  due  to  the  necessity  of  heating 
up  the  kiln  for  each  burning.  Saylor  burned  his  first  Portland 
cement  in  these  kilns  and  the  first  mills  in  the  Lehigh  Valley  all 
used  this  form  of  kiln.  In  Europe  where  the  bricks  were  made 


KILNS  AND  BURNING 


IOI 


from  the  more  or  less  plastic  mixture  of  chalk  and  clay  no  diffi- 
culty was  experienced  in  forming  the  bricks ;  in  this  country,  how- 
ever, the  fine  crystalline  cement  rock  did  not  have  sufficient  bind- 
ing power  of  itself  to  make  bricks  of  the  strength  to  withstand  the 
weight  of  the  charge  above  them  in  the  kilns,  and  it  was  found 
necessary  to  incorporate  with  it  a  small  proportion  of  Portland 
cement,  to  give  it  binding  power.  At  the  American  Cement  Co.'s 
plant  at  Egypt,  Pa.,  the  fine  powder  was  mixed  with  liquid  hydro- 
carbons to  form  a  stiff  paste,  which  was  moulded  by  compression 
into  bricks.  This  process  saved  drying  the  bricks  and  promised 
well,  when  the  introduction  of  water  gas  raised  the  price  of  coal 
tar,  and  necessitated  the  abandonment  of  the  scheme. 

The  first  efforts  made  to  improve  the  "bottle"  kiln  were  natu- 
rally to  use  the  waste  heat  in  the  products  of  combustion  coming 
off  at  the  mouth  of  the  kiln  for  drying  the  bricks.  Fig.  18  shows 


Fig.  18.    Johnston  Kiln. 

the  form  of  kiln  invented  in  1872,  by  Mr.  I.  C.  Johnston,  of 
Greenhithe,  England,  for  this  purpose.  A  is  the  kiln  and  B  is  the 
drying  chamber.  The  kiln  is  charged  with  the  bricks  which  have 
been  dried  by  the  heat  of  the  previous  burn.  The  wet  bricks  for 
the  next  charge  are  placed  at  the  same  time,  in  the  tunnel-shaped 
flue  and  the  hot  gases  from  the  kiln  pass  over  and  around  them, 
and  dry  them  thoroughly.  These  kilns  are,  of  course,  more  sat- 
isfactory than  the  ordinary  "bottle"  kiln,  but  they  still  waste  much 
heat.  The  hot  clinker,  of  course,  carries  off  a  great  deal,  and  the 
cooling  off  of  the  kiln  itself  causes  additional  waste.  These  kilns 
were  installed  in  the  original  mill  of  the  Western  Portland  Ce- 


102 


PORTLAND  CEMENT 


ment  Co.,  Yankton,  S.  D.  The  time  lost  in  drawing  the  clinker, 
charging  the  kiln  and  heating  it  up,  as  well  as  the  heat  losses,  led 
to  the  design  of  continuous  kilns,  in  which  the  charging  is  car- 
ried on  continuously  at  the  top,  and  the  clinker  is  drawn  off  from 
time  to  time  at  the  bottom.  Among  the  best  known  of  these  kilns 
are  the  Hoffmann  ring  kiln,  the  Schoefer  and  the  Deitsch  kilns, 
the  latter  two  are  modifications  of  the  etagen-ofen  or  kiln  of  sev- 
eral stories.  These  kilns  are  all  economical  of  fuel,  but  all  re- 
quire the  material  to  be  made  into  bricks  for  burning  and  the 
clinker  to  be  sorted. 

The   Hoffmann   kiln    is    shown    in    Fig.    19.      It    consists    of 


Fig.  19.     Hoffmann  Ring  Kiln. 


a    ring    of    chambers,    built    around    a    large    central    chimney. 
Each    chamber    is    connected    with    the    chimney    by    a    flue 


KILNS  AND  BURNING  IO3 

and  has  a  door  opening  outwards.  The  chambers  are  also 
all  connected  with  each  other.  The  bricks  are  piled  up  in 
the  chambers,  just  as  they  are  in  a  brick  kiln,  so  that  the  products 
of  combustion  can  pass  around  them  and  between  them.  The 
oven  is  operated  as  follows :  When  a  chamber  is  loaded,  it  is 
shut  off  from  the  succeeding  one,  which  is  empty,  by  a  sheet  iron 
door,  and  connected  with  the  preceding  one.  The  flue  leading 
into  the  chimney  is  also  opened  and  the  corresponding  flue  in  the 
preceding  chamber  is  closed.  By  this  means,  the  waste  heat 
from  the  compartment,  whose  contents  is  being  burnt,  is  passed 
forward,  around  the  ring  of  compartments,  to  the  one  just 
charged,  and  thence  through  the  flue  and  up  the  chimney.  By 
this  means  the  contents  of  the  chambers  are  gradually  heated  up, 
the  bricks  are  dried  in  the  chambers  near  the  flue  and  then  be- 
come hotter  and  hotter  as  the  chamber  of  combustion  is  brought 
nearer.  The  air  for  burning  is  passed  through  the  chambers  in 
which  burning  is  completed  and  is  thereby  itself  heated  and  the 
clinker  cooled.  It  is  usual  to  load  one  compartment  each  day,  and 
of  course,  to  draw  one.  The  fuel  for  burning  is  not  loaded  in 
with  the  bricks,  but  is  fed  in  from  openings  at  the  top  of  the  kiln 
during  burning.  The  Hoffmann  kiln  is  very  economical  of  fuel, 
but  requires  much  skilled  labor  if  it  is  to  be  operated  successfully. 
The  bricks  have  to  be  carefully  piled  and  the  charging  requires 
skilled  hands.  This  kiln  is  much  in  use  in  Germany,  but  so  far 
as  the  writer  knows,  has  never  been  used  in  this  country  for  burn- 
ing Portland  cement. 

The  Dietsch  kiln  is  shown  in  Fig.  20.  It  was  patented  in  1884. 
It  consists  of  a  cooling  chamber  H,  a  burning  chamber  F  and  a 
heating  chamber  C.  The  kilns  are  usually  built  in  pairs,  back  to 
back.  The  kiln  is  loaded  through  the  door  A,  and  as  clinker  is 
drawn  out  at  the  bottom,  the  dry  slurry  drops  down  into  the  heat- 
ing chamber  where  it  is  gradually  brought  up  to  a  high  tempera- 
ture. From  the  heating  chamber  it  is  raked  over  into  the  combus- 
tion chamber,  by  introducing  a  tool  in  the  door  £,  and  fuel  for 
the  burning  is  mixed  with  it  through  the  same  door.  The  burning 
is  completed  in  F.  The  cold  air  for  combustion  is  heated  by  pass- 
ing through  the  red  hot  clinker  in  H,  cooling  the  latter.  Eyes 


KILNS  AND   BURNING 


105 


are  placed  at  the  lower  levels  of  the  combustion  chamber,  through 
which  bars  may  be  inserted  to  detach  the  sintered  mass  should  it 
hang  up,  due  to  overburning.  The  Deitsch  kiln  is  also  econom- 
ical of  fuel,  but  does  not  require  the  slurry  to  be  made  into  bricks. 
Several  were  introduced  into  this  country  in  the  early  days  of  the 
industry,  one  being  built  for  the  Buckeye  Portland  Cement  Co., 


Fig.  21.     Schoefer  Kiln. 


of  Bellefontaine,  O.  A  modification  of  the  Deitsch  kiln  perfected 
in  Denmark  and  known  as  the  Schoefer  kiln,  was  introduced  into 
several  of  the  earlier  cement  mills  and  was  used,  I  believe,  by 


IO6  PORTLAND  CEMENT 

the  Glens  Falls  Portland  Cement  Co.,  Glens  Falls,  N.  Y.,  exclu- 
sively, and  also  by  the  Coplay  Cement  Co.,  at  one  of  their  mills,  at 
Coplay,  Pa.,  where  eleven  were  once  in  use.  The  Schoefer  kiln 
is  shown  in  Fig.  21.  It  operates  upon  the  same  principle  as  the 
Deitsch  kiln  and  consists  of  a  long  vertical  flue,  the  upper  part 
of  which  serves  as  a  preheating  chamber,  the  middle  narrow  part 
as  a  combustion  chamber  and  the  lower  section  to  heat  the  draft. 
With  all  of  these  kilns  the  product  has  to  be  sorted  and  the 
underburned  portions  picked  out  and  reburned.  They  are  also 
troubled  with  dusting  clinker: — that  is,  clinker  which  falls  to  a 
powder  on  cooling.  This  fault  is  supposed  to  be  caused  by  burn- 
ing with  a  reducing  flame  due  to  the  formation  of  carbon  mon- 
oxide from  either  incomplete  combustion  or  decomposition  of  the 
carbon  dioxide  by  the  red  hot  coke.  These  shaft  kilns  require 
only  about  45  pounds  of  coal  per  barrel,  but  the  labor  cost  con- 
nected with  them  is  two  or  three  times  as  great  as  the  fuel  cost. 
The  shaft  kilns  themselves  cost  about  as  much  as  a  rotary  kiln, 
but  only  turn  out  about  half  as  much  clinker. 

The  Rotary  Kiln. 

The  kilns  above  described  are  still  used  largely  in  Ger- 
many; in  France  and  Belgium,  the  Candlot  and  Bauchere 
kilns  are  used,  and  in  England  the  Johnston  kiln  is  much 
employed.  In  this  country  the  cost  of  moulding  the  raw 
material  into  bricks  was  considerable,  and  the  sorting  of 
the  clinker,  made  necessary  by  the  uneven  burning  in 
these  kilns,  further  increased  the  cost  of  manufacture.  Abroad 
where  labor  is  much  cheaper  than  it  is  in  this  country,  these  oper- 
ations could  be  carried  on  successfully,  so  that  European  cements 
could  be  brought  to  this  country  and  sold  in  competition  with 
American  cements  at  a  good  profit.  Their  reputations  were  es- 
tablished and  they  could  successfully  hold  their  market  against 
the  home  manufacturers,  who  could  not  afford  to  cut  the  price 
of  their  cement  owing  to  the  high  cost  of  manufacturing  due  to 
the  expensive  labor  item,  so  that  all  the  early  manufacturers  were 
seeking  a  cheaper  method  of  burning,  one  that  would  do  away 
with  the  employment  of  so  much  hand  labor  and  allow  them  to 
compete  successfully  with  their  foreign  rivals.  This  led  them  to 


KILNS  AND  BURNING  IO/ 

experiment  with  the  rotary  kiln  which  had  been  invented  in  1873 
by  F.  Ransom,  an  English  engineer,  but  which  had  never  been 
successfully  used  in  England.  In  this  country  the  first  plant 
to  attempt  its  use  was  a  small  plant  in  Oregon1,  in  1887,  but 
the  attempt  proved  a  failure  and  the  plant  itself  was  shut  down, 
owing  to  litigation  among  its  stockholders.  About  the  same  time 
the  Atlas  Portland  Cement  Co.  began  to  experiment  with  Ran- 
som's kiln  at  first  at  East  Kingston,  New  York,  on  wet  mate- 
rials and  la'ter  with  success  upon  the  cement  rock  of  the  Lehigh 
District  at  Northampton.  At  first  they  met  with  many  diffi- 
culties, and  it  was  only  after  much  experimenting,  that  they  suc- 
ceeded in  making  it  work  successfully.  They  found  that  owing 
to  the  shorter  time  during  which  the  material  underwent  calcina- 
tion, it  was  necessary  to  grind  it  much  finer  than  had  been  neces- 
sary with  the  old  bottle  shaped  kilns.  They  also  found  it  neces- 
sary to  carry  the  lime  a  little  higher,  in  their  raw  material  than 
had  been  done  before,  and  to  moisten  it  slightly  with  water.  It  is 
undoubtedly  true  that  to  the  Atlas  Portland  Cement  Co.  and  to  its 
officials,  Navarro,  Giron,  Seaman  and  Hurry,  the  credit  of  the 
commercial  development  of  the  rotary  kiln  is  due.  In  Ransom's 
original  patent  he  proposed  to  heat  the  kiln  by  producer  gas,  but 
its  development  in  this  country  was  made  possible,  by  the  use  of 
crude  oil,  as  a  successful  method  of  burning  powdered  coal  had 
not  been  perfected  at  that  time.  At  first  these  kilns  were  only  40 
feet  long,  but  it  was  soon  found  more  economical  to  lengthen 
them,  60  feet  being  now  the  usual  length. 

The  rotary  kiln  in  its  usual  form  consists  of  a  cylinder,  6  feet 
in  diameter  by  60  feet  long,  made  of  steel  sheets  from  y2  to  9/16 
inches  in  thickness,  lined  with  fire  brick.  The  steel  sheets  are 
held  together  with  single  strap  butt  joints,  as  these  joints  resist 
expansion  strains  due  to  heating  better  than  lap  joints.  This  cyl- 
inder is  supported  at  a  very  slight  angle  from  the  horizontal  on 
two  tires  made  of  rolled  steel,  and  having  a  6-inch  face  and  a 
thickness  of  at  least  4  inches.  These  tires  are  not  fastened  direct- 
ly to  the  kiln,  but  are  held  4  to  6  inches  from  the  latter  by  an 
arrangement  of  blocks  and  plates.  They  run  each  on  four  heavy 

i  Mineral  Resources,  U.  S.  Geol.  Survey,  1887,  p.  530. 


IO8  PORTLAND  CEMENT 

friction  rollers  usually  mounted  in  pairs  on  a  rocker  and  made 
of  cast  steel.  The  kiln  is  driven  by  a  girth  gear  situated  usually 
near  its  middle,  and  a  train  of  gears,  actuated  either  by  a  line 
shaft  or  a  motor.  The  upper  end  of  the  kiln  projects  into  a 
brick  flue  which  is  surmounted  by  a  steel  stack.  The  flue  is  pro- 
vided with  a  door  at  the  bottom  to  take  out  the  dust  which  ac- 
cumulates there.  Dry  material  is  fed  into  the  kiln  by  means  of  a 
water- jacketed  screw  conveyor  running  from  the  kiln  bins,  which 
are  situated  usually  just  back  of  the  flue,  through  the  latter,  far 
enough  into  the  kiln  to  prevent  the  materials  falling  into  the  flue 
when  the  kiln  revolves.  The  feeding  device  is  usually  attached 
to  the  driving  gear  of  the  kiln,  so  that  when  the  latter  stops  the 
feed  is  shut  off.  When  slurry  is  used,  this  is  pumped  into  the  kiln 
from  a  vat  below,  by  either  a  plunger  pump  or  compressed  air. 
In  some  instances,  it  is  pumped  against  the  pressure  of  a  stand- 
pipe,  to  insure  a  constant  feed.  The  lower  end  of  the  kiln  is 
closed  by  a  hood  into  which  the  kiln  projects.  Some  times  this 
hood  is  made  stationary  with  movable  fire  brick  doors,  but  oftener 
it  is  mounted  on  a  movable  carriage.  The  front  wall  of  the  hood 
is  provided  with  two  holes,  one  for  the  entrance  and  support  of 
the  burning  apparatus,  and  the  other  for  observing  the  operation 
of  the  kiln  and  for  inserting  bars  to  break  up  the  rings  formed 
and  repair  the  lining.  The  lower  part  of  the  hood  is  left  partly 
open,  and  through  this  the  clinker  falls.  Air  for  combustion  also 
enters  here.  Figs.  22  and  23  show  as  well  as  can  be  done  in  a 
small  illustration  of  such  a  long  object  the  construction  of  the 
completed  kiln. 

The  usual  diameter  of  a  6ofoot  rotary  kiln  unlined  is 
from  6  to  7  feet.  Most  of  them  are  made  the  same  diam- 
eter throughout,  though  some  of  them  are  made,  say  6  feet 
6  inches  in  diameter  for  the  first  30  feet  and  then  taper 
through  10  feet  to  a  diameter  of  5  feet  6  inches  for  the 
remaining  20  feet;  others  taper  for  the  last  10  or  15 
feet  before  entering  the  stack.  This  latter  plan  has  the  ef- 
fect of  a  damper,  crowding  the  heat  more  to  the  front  of  the 
kiln.  It  probably  lessens  the  output  somewhat,  since  the  choking 
cuts  down  the  amount  of  coal  that  can  be  burned,  but  it  probably 


btt 


KILNS  AND  BURNING  IOQ 

also  adds  something  to  the  economy  of  the  process.     Some  kilns 


are  made  to  bear  on  three  tires,  but  the  usual  plan  for  a  60- foot 
kiln  is  but  two  tires. 


no 


PORTLAND  CEMENT 


Fig.  24  shows  an  arrangement  designed  by  the  Allis-Chalmers 
Co.  for  feeding  the  material  into  the  kiln  by  means  of  a  water- 
jacketed  conveyor.  It  is  also  possible  by  moving  the  stack  to  one 
side  or  behind  the  flue  to  spout  the  material  into  the  kiln  through 
an  asbestos-covered  spout. 


Fig.  24.     Stock  Bins  and  Water  Jacketed  Conveyor  for  Feeding  Raw  Material 
into  the  Kiln. 

The  kilns  are  rotated  at  different  mills  at  different  speeds,  vary- 
ing from  one  turn  in  one-half  a  minute  to  one  turn  in  three.  The 
average,  however,  is  from  a  turn  in  a  minute  and  a  half  to  one 
in  two  minutes.  Usually  the  speed  can  be  regulated  by  some  ar- 
rangement of  an  automatic  speeder,  such  as  the  Reeves,  the 
Mosser  speeder  or,  where  run  from  separate  motors,  by  a  con- 
troller. In  some  mills  all  the  kilns  are  on  one  shaft  and  conse- 


KILNS  AND  BURNING 


III 


quently  of  fixed  speed.  There  are  some  points  in  favor  of  each. 
Where  the  speed  can  be  regulated  by  the  burner,  he  has  better 
control  of  the  burning,  but  there  is  sometimes  a  tendency  on  his 
part,  where  the  foreman  is  lax,  to  cut  down  the  speed  and  conse- 
quently the  capacity  of  the  kiln  in  order  to  make  his  own  work 
easier.  Where  there  is  a  likelihood  of  the  mix  not  being  regular, 
speeders  should  always  be  put  in,  as  it  is  easier  to  control  the 
burning  of  such  material  by  the  kiln  speed  than  by  the  coal  feel. 
Writh  fixed  speed,  the  kilns  are  arranged  with  some  sort  of  jaw 
clutch,  so  they  can  be  cut  out  for  patching,  relining,  etc.  It  is 
also  necessary  occasionally  to  shut  them  down  for  "heat"  if  the 


Fig.  25.    Method  of  Burning  Powdered  Coal.     (B.  F.  Sturtevant  Co.) 

mixture  burns  hard,  or  the  raw  material  is  fed  into  the  kiln  irreg- 
ularly, causing  it  to  become  overloaded.  As  we  have  said,  the 
raw  material  fed  into  the  kiln  should  be  controlled  by  its  speed 
and  be  shut  oft'  when  the  kiln  stops.  A  great  deal  has  been  said 
about  the  proper  speed  for  a  kiln  to  revolve,  no  two  authorities 
agreeing,  and  the  writer  has  come  to  the  conclusion  from  personal 


112  PORTLAND  CEMENT 

experience  that  this  will  depend  largely  upon  the  material,  how 
it  burns,  etc. 

Fuel. 

As  we  have  said,  during  the  early  experiments. with  the  rotary 
kiln,  crude  oil  was  used  as  a  fuel.  The  growing  scarcity  and 
high  price  of  oil  led  to  the  abandonment  of  this  as  a  fuel  and  the 
substitution  of  powdered  coal  in  its  place.  This  practice  became 
general  about  1899,  and  since  this  cheap  form  of  fuel  was  intro- 
duced, no  new  plants  have  been  built  which  did  not  install  rotary 
kilns,  the  objection  to  them  previous  to  this  being  the  high  cost 
of  the  oil.  The  saving  effected  by  the  change  was  considerable, 
and  only  one  or  two  plants  in  this  country  use  crude  oil,  and  these 
are  situated  near  oil  fields. 

The  method  for  burning  the  powdered  coal  is  shown  in  Fig.  25. 
It  consists  of  an  injector  through  which  air  is  forced  by  a  fan. 
The  coal  is  conveyed  out  of  a  bin  by  a  screw  conveyor,  falls  into 
the  injector,  is  sucked  in  and  mingles  with  the  air  as  it  passes 
through  the  pipe  to  the  kiln.  The  injector  is  usually  of  cast  iron, 
the  pipe  leading  to  the  kiln  is  of  galvanized  iron  and  terminates 
in  a  nozzle  of  wrought  iron  pipe,  which  projects  for  a  foot  or 
more  through  the  hood  into  the  kiln.  The  screw  conveyor  lead- 
ing from  the  bin  is  run  usually  by  a  line  shaft  independent  of  the 
kilns  and  usually  attached  to  the  fans  or  the  motor  driving  the 
fans.  The  connection  with  the  shaft  is  made  either  by  some  form 
of  speed  controller,  or  else  by  a  stepped  pulley,  so  the  coal  feed 
can  be  regulated.  The  air  blown  in  is  constant  and  is  only  a 
fraction  of  that  needed  for  combustion.  In  some  mills  air  from 
the  compressors  or  high  pressure  air  is  used,  and  in  others  a 
combination  of  the  two  is  sought.  The  main  object  in  any  event 
is  merely  to  carry  the  coal  into  the  kiln  and  to  get  a  good  mixture 
of  coal  and  air. 

Fig.  26  A  shows  the  construction  of  an  injector  for  use  with  low 
pressure  air,  and  Fig.  26  B  one  for  use  with  high  pressure  air. 

The  degree  of  fineness  to  which  the  coal  is  ground  affects  the 
amount  of  coal  used  directly,  the  finer  the  coal  the  less  will  be 
needed.  Spackman  stated  in  a  paper  read  before  the  Association 
of  Portland  Cement  Manufacturers  that  a  fineness  increase  of  io 


KILNS  AND  BURNING 


over  7$%  through  a  2OO-mesh  sieve  would  effect  a  saving  of  2% 
in  fuel.  This  has  been  the  experience,  I  believe,  in  other  lines 
than  cement  in  which  powdered  coal  has  been  tried. 


Fig.  26  A.  High  Pressure  Coal  Burner. 
(C,  coal  ;  H.  P.  A.,  high  pressure  air  ; 
A.  A.,  atmospheric  air.) 


Fig.  26  B. 


As  to  the  fuel  consumption  of  the  rotary  kiln,  many  reports 
seem  to  show  that  the  6x6o-foot  rotary  kiln  will  require  upon  dry 
material  from  96  to  no  Ibs.  of  dry  coal  on  an  average,  counting 
all  the  coal  burned,  including  that  for  heating  the  kiln  after 
patching  and  the  usual  enforced  shut-downs  and  delays.  Upon 
wet  materials  the  coal  consumption  is  from  140  to  160  Ibs.  per 
barrel.  The  extra  coal  being  needed  for  the  evaporation  of  the 
water  of  the  slurry. 


114  PORTLAND  CEMENT 

The  coal  for  burning  is  usually  gas  slack  and  should  fill  the 
specifications  below : 

Volatile  and  combustible  matter 30-45  % 

Fixed  Carbon 45-60% 

Ash  not  over 10% 

Sulphur  has  no  effect  on  the  burning,  except  in  large  quanti- 
ties. Iron  pyrites  are  hard,  and  consequently  may  not  pulverize. 
When  coal  containing  much  of  this  is  used  the  pyrites  may  re- 
main in  coarse  crystals  after  grinding,  which  are  not  blown  in 
the  kiln  and  burned,  but  fall  from  the  nozzle  of  the  burner  among 
the  clinkers  and  remaining  unoxidized,  are  ground  with  the  clink- 
er, causing  the  resulting  cement  to  develop  brown  stains.  Prac- 
tically none  of  the  sulphur  of  the  coal  enters  the  cement,  except 
as  above. 

Grinding  the  Coal. 

The  coal  for  burning  is  usually  crushed  in  pot  crushers  or  be- 
tween rolls,  dried  in  a  special  form  of  rotary  dryer  and  finely  pul- 
verized in  tube  mills  or  Griffin  mills.  In  some  mills  using  a  tube 
mill,  this  is  preceded  by  a  ball  mill  or  a  Williams  mill ;  and  in 
some,  the  coal  is  sent  direct  from  the  pile  to  the  dryers  and  thence 
through  the  rolls. 

One  of  the  best  forms  of  pot  crushers  is  what  is  known  as  a 
"coffee-mill  cracker."  This  is  shown  in  Fig.  27.  It  works  upon 
the  same  principle  as  a  coffee-mill,  and  its  action  is  a  grinding 
one  due  to  the  toothed  spindle,  rather  than  a  crushing  one,  and 
hence  it  can  not  choke  up  with  soft  material  as  a  gyratory  crusher 
would  do. 

When  a  set  of  rolls  is  placed  before  the  dryer  they  are  of  the 
toothed  form  shown  in  Fig.  28  and  can  be  used  to  crush  run  of 
mine  coal.  These  rolls  have  a  face  about  30  inches  wide  and  are 
usually,  about  24  inches  in  diameter.  Where  rolls  are  placed  after 
the  dryer  to  prepare  coal  for  the  tube  mill  they  should,  however, 
be  plain-faced  or  very  slightly  corrugated.  The  toothed  rolls  will 
reduce  coal  to  a  size  of  I  or  2  inch  lumps  and  the  plain-faced  rolls 
will  crush  to  lumps  ranging  from  y2  inch  down. 

Three  or  four  forms  of  coal  dryers  are  in  common  use  for  dry- 
ing coal  for  cement  burning.  The  common  form  consists  of  a 


Fig.  27.     "Coffee  Mill  Cracker"  or  Pot  Crusher. 


Fig.  28.     Coal  Crushing  Rolls 


KILNS  AND  BURNING 


rotary  cylinder  provided  with  shelves,  and  in  general  similar  to 
the  dryers  used  for  rock ;  except  that  it  is  encased  in  brick  work 
and  that  the  products  of  combustion  pass  around  them  and  then, 
after  cooling  somewhat,  back  through  them,  instead  of  directly 
through  them  as  with  the  rock  dryers.  Other  forms  of  coal  dry- 
ers are  those  manufactured  by  the  F.  D.  Cummer  &  Son  Co.,  The 
Ruggles-Coles  Engineering  Co.,  and  The  Bartlett  &  Snow  Co. 
The  Ruggles-Coles  dryer  is  shown  in  Fig.  29,  and  consists  of 


Fig.  29.     Ruggles-Coles  Dryer. 

two  concentric  cylinders,  which  are  fastened  together  and  revolve 
on  steel  tires,  supported  by  bearing  wheels.  The  cylinders  are 
driven  by  gearing  as  shown.  The  inner  cylinder  extends  beyond 
the  outer  one  at  the  head  end,  and  is  connected  with  a  brick  fur- 
nace by  a  flue  lined  with  fire  brick.  The  products  of  combustion 
from  the  furnace  pass  down  the  central  flue,  and  then  back  be- 
tween the  two  cylinders.  The  coal  is  fed  into  the  head  end  of  the 
dryer  between  the  two  shells,  and  is  caught  up  by  flights  on  the  in- 
side of  the  outer  shell  and  dropped  on  the  hot  inner  shell.  As  the 
machine  revolves  the  coal  drops  from  the  inner  shell  to  the  bottom 
of  the  outer  one,  is  carried  up  by  the  flights  and  again  dropped  on 
the  hot  inner  shell,  etc.,  until  dried.  The  hot  gases  of  combustion 
passing  up  between  the  two  shells  also  help  to  dry  the  material, 
which  is  discharged  through  the  centre  of  the  rear  end.  The  fan 
is  used  to  create  a  draft  through  the  cylinders.  These  dryers  are 


u6 


PORTLAND  CEMENT 


very  economical  and  have  been  known  to  give  as  high  economy 
as  7  to  8  Ibs.  of  water  evaporated  per  pound  of  coal  burned. 

The  Cummer  dryer  is  shown  in  Fig.  30.  It  consists  of  an  iron 
cylinder  entirely  surrounded  by  a  brick  chamber.  The  cylinder 
is  set  at  an  incline  and  revolves  on  trunnioned  bearings.  It  is 
provided  with  a  great  many  hooded  openings,  ] ,  so  arranged  that 
the  heated  air  and  gases  of  combustion  are  drawn  into  the  cylin- 
der by  means  of  the  fan,  G.  A  furnace  provided  with  a  mechan- 
ical stoker  produces  the  heat.  The  hot  gases  are  drawn  into  the 
brick  work  chamber,  where  they  are  mingled  with  air  drawn  in 


/-    *  •  -y 


Fig.  30.     Cummer  Dryer. 

through  the  registers,  £  and  O,  located  at  intervals  in  the  brick 
work  side  of  the  chamber,  and  their  temperature  reduced  by  the 
dilution  to  a  point  making  it  safe  for  them  to  come  in  contact  with 
the  coal.  The  mingled  air  and  gases  of  combustion  are  then 
drawn  through  the  openings,  /,  and  up  through  the  cylinder.  The 
material  is  fed  into  the  cylinder  through  the  hopper,  F,  and  parts 
with  its  moisture  as  it  works  its  way  down  through  the  cylinder 
to  the  discharge,  K. 

At  the  plant  of  the  International  Portland  Cement  Co.,  Hull, 
Canada,  the  coal  is  dried  by  drawing  air  over  the  red  hot  cement 
clinker,  and  then  through  an  ordinary  dryer  (such  as  is  used  for 
rock)  with  a  fan.  This  serves  to  both  cool  the  clinker  and  dry 
the  coal. 

When  Griffin  mills  are  used  to  pulverize  the  coal  it  is  usual  to 


KIIvNS  AND  BURNING  117 

reduce  the  latter  to  */2  inch  size,  though  these  mills  are  used  occa- 
sionally on  gas  slack  taking  it  just  as  it  comes  from  the  pile. 
Tube  mills  require  the  coal  to  be  crushed  by  rolls  or  a  crusher. 
In  a  few  instances,  ball  mills  have  been  installed  to  do  this  work, 
but  have  generally  proved  unsatisfactory  from  the  frequency  with 
which  the  outer  screens  clog.  Two  excellent  mills  for  preparing 
coal  for  the  tube  mill  are  the  Williams  mill  and  the  Stedman  cage 
disintegrator.  The  Williams  mill  is  shown  in  Fig.  31  and  con- 
sists of  hinged  hammers  which  revolve  rapidly  around  a  horizon- 
tal shaft.  These  crush  the  material,  and  it  passes  out  through  a 
screen  as  shown  in  the  cut. 


Fig.  31.     Williams  Mill. 

Coal  for  burning  Portland  cement  should  be  so  finely  ground 
that  at  least  92%,  and  better  95  %  of  it,  should  pass  a  No.  100 
sieve.  The  fineness  is  tested  by  sieving  as  directed  for  testing 
the  fineness  of  cement,  using  shot  to  rap  the  coal  through  the 
sieve. 

A  Griffin  mill  will  grind  coal  from  rolls  to  a  fineness  of  95% 
through  a  zoo-mesh  screen  at  the  rate  of  about  \y2  to  2  tons  per 
hour  and  at  an  expenditure  of  20-25  horse-power.  A  5'  6"x2o' 
tube  mill  will  grind  enough  coal  for  a  six  kiln  plant,  or  about  2^ 
tons  per  hour,  taking  coal  ranging  from  y2  inch  lumps  down,  and 
using  80  horse-power  in  doing  so.  The  Williams  mill  is  made  in 


Il8  PORTLAND  CEMENT 

several  sizes  and  one  large  enough  to  prepare  coal  for  two  tube 
mills  can  be  obtained.  The  capacity  of  a  coal  grinding  plant  will 
depend  entirely  on  the  condition  in  which  the  coal  is  received  at 
the  mill  and  the  thoroughness  with  which  the  coal  is  prepared  for 
the  tube  mill  or  Griffin  mill.  The  tube  mill  is  not  well  adapted 
to  crushing  coarse  material  and  where  it  is  used  considerable 
economy  will  be  effected  by  reducing  the  coal  to  y<\  inch  or  finer 
by  means  of  some  form  of  disintegrator  such  as  a  Williams  or 
Stedman  mill.  When  run  of  mine  coal  is  received,  the  best  treat- 
ment would  be  by  a  set  of  toothed  rolls  before  the  dryer,  then  the 
dryer,  followed  by  a  disintegrator  and  a  tube  mill  or  by  a  set  of 
plain-faced  rolls  and  a  Griffin  mill. 

In  order  to  avoid  dangerous  explosions  in  coal  mills,  the  roof 
should  be  so  ventilated  that  there  can  be  no  accumulation  of  gases 
here.  The  precautions  about  lights,  fire,  smoking  by  the  opera- 
tors, etc.,  that  are  usually  taken  in  connection  with  inflammable 
materials  should  also  be  observed.  When  tube  mills  catch  on  fire 
inside,  the  fire  may  be  smothered  with  steam ;  or  a  2O-lb.  drum  of 
liquid  carbon  dioxide  gas  may  be  kept  and  used  for  this  purpose. 
The  mill  must  be  well  cleared  of  this  gas,  however,  before  work- 
men are  allowed  to  enter  it  to  prevent  their  asphyxiation.  Water 
is  ineffective  and  should  not  be  used  as  it  merely  stirs  up  a  dust, 
and  mixtures  of  coal  dust  and  air  are  very  explosive. 

O.  A.  Done,  writing  in  Engineering  News,  gives  the  following 
hints  on  the  prevention  of  spontaneous  ignition  in  coal  piles.  The 
amount  of  moisture  in  a  bituminous  coal  is  a  measure  of  the  risk 
of  spontaneous  combustion  when  the  fuel  is  stored.  Bituminous 
coal  should  not  contain  more  than  4.75  per  cent,  water.  Coal 
bins  should  be  of  steel  or  iron  protected  by  concrete  and  should 
be  roofed  over.  Free  air  passages  should  be  provided  around  the 
walls  and  beneath  the  bins  to  keep  the  pile  cool,  and  the  depth  of 
the  coal  should  never  exceed  12  feet.  It  is  useless  to  provide  air 
passages  in  the  body  of  the  pile  as  these  only  tend  to  promote 
oxidation;  similarly  cracks,  etc.,  in  the  walls  of  the  fuel  bin  in- 
crease the  risk. 

Burning  with  Natural  and  Producer  Gas. 

Natural  gas  has  been  successfully  used  for  the  heating  of  the 


KILNS  AND  BURNING 


119 


kiln,  both  at  lola,  Kan.,  and  at  Wampum,  Pa.  At  the  former 
place  the  gas  is  also  used  to  generate  power  for  grinding,  etc.,  in 
gas  engines.  Producer  gas  has  been  tried  but  the  writer  knows  of 
but  one  plant  where  it  has  been  used  for  any  great  length  of  time, 
that  is  at  a  small  plant  in  Canada.  In  conversation,  the  man- 
ager of  this  plant  informed  the  author  that  they  considered  it  as 
cheap  as  powdered  coal,  but  saw  no  particular  advantage  in  its 
use.  The  question  has  been  raised  at  numerous  times  as  to  whether 
sufficient  heat  could  be  developed  by  its  use  to  secure  the  proper 
temperature  in  the  kiln  for  burning,  and  numerous  calculations 


Fig.  32.     Swindell  Gas  Producer  and  Rotary  Kiln. 

have  been  given  to  prove  that  without  regeneration  producer  gas 
could  not  be  used  for  burning  Portland  cement.  The  fact  that  it 
is  used  at  this  plant  should  effectually  set  at  rest  this  contention. 
At  this  plant,  the  producers  are  located  directly  in  front  of  the 
kilns  and  below  the  kiln  floor,  the  gas  being  conducted  to  the  kiln 
by  a  short  pipe. 


I2O  PORTLAND  CEMENT 

The  Diamond  Portland  Cement  Co.,  Middle  Branch,  O.,  has 
also  had  a  Swindell  gas  producer  in  operation  heating  one  of  their 
kilns  for  over  a  year  and  they  report  very  favorably  upon  its  use. 
Fig.  32  shows  the  installation  of  the  producer  at  this  plant.  The 
gas  producer  is  built  15  feet  in  front  of  the  kiln,  which  is  6  feet 
in  diameter  and  60  feet  long.  The  coal,  which  is  of  inferior  qual- 
ity and  costs  only  $1.50  per  ton,  is  introduced  into  the  producer 
by  means  of  sliding  hoppers.  Steam  and  air  are  introduced  under 
and  through  the  inclined  grates  by  means  of  blowers.  The  ail/ 
used  for  combustion  is  preheated  by  passing  up  through  iron 
tubes  built  in  the  walls  of  the  producer.  The  air  and  gas  are  led 
to  the  kiln  by  separate  flues  as  shown  in  the  plan.  The  labor  re- 
quired to  operate  the  producers  amounts  to  about  3^/2  cents  per 
barrel  of  cement  including  the  wages  of  the  burners,  the  coal 
consumption  amounts  to  130  Ibs.  per  barrel  and  the  output  to  240 
barrels  per  day. 

The  producer,  however,  has  not  yet  reached  anything  near  like 
perfection.  The  development  of  the  gas  engine  will  also  have  a 
direct  bearing  on  the  question.  If  this  should  be  brought  to  the 
point  where  it  would  displace  steam,  the  gas  producer  would  be 
much  improved  and  the  possibility  of  generating  gas  for  burning 
and  for  power  in  one  and  the  same  plant,  doing  away  with  boil- 
ers and  coal  grinding  machinery,  would  undoubtedly  influence 
manufacturers  largely  in  putting  in  producers.  The  gas  engine  is 
being  perfected  rapidly  and  results  obtained  in  Europe  lead  one 
to  believe  its  commercial  perfection  will  be  shortly  accomplished. 

Mr.  H.  F.  Spackman,  in  a  paper  read  at  a  meeting  of  the  Ce- 
ment Manufacturers'  Association,  stated  that  in  a  plant  designed 
by  his  company  producers  were  tried  in  connection  with  powdered 
coal  on  two  rotary  kilns,  60  feet  long  by  5  feet  in  diameter,  burn- 
ing slurry  containing  60%  water.  Actual  figures  in  this  plant  ob- 
tained on  a  two  or  three  months'  run,  were  125  barrels  of  cement 
per  day,  with  a  coal  consumption  of  135  Ibs.  of  coal  per  barrel, 
while  the  kilns  working  on  powdered  coal  required  on  an  average 
for  a  seven  months'  run  138  Ibs.  of  coal  per  barrel.  To  greatly 
overbalance  this  3  Ibs.  saving  in  coal,  however,  was  the  fact  that 
six  men  each  shift  of  24  hours  were  required  to  work  the  pro- 


KILNS  AND  BURNING  121 

ducers  and  that  as  gas  slack  could  not  be  employed  a  coal  costing 
50  cents  more  a  ton  had  to  be  substituted. 

Natural  gas  is  used  for  burning  cement  at  several  plants  in 
Kansas.  Its  use  has  passed  beyond  the  experimental  stage  and 
where  it  is  obtainable  it  is  of  course  the  cheapest  form  of  fuel. 
Natural  gas  is,  however,  found  in  too  few  localities  to  make  it 
generally  applicable  to  cement  burning,  and,  even  when  found, 
the  supply  is  limited  and  may  give  out  after  a  few  years.  Below 
are  analyses  of  the  gas  at  Tola,  Kans.,  and  at  Independence, 
Kans.,  at  both  of  which  places  Portland  cement  mills  are  using 
natural  gas  not  only  for  heating  the  kilns  but  also  for  generating 
power. 

ANALYSIS   OF  NATURAL   GAS   USED   FOR   BURNING  PORTLAND 
CEMENT  IN  KANSAS  (BAILEY).1 

lola.  Independence. 

Hydrogen o.oo  o.oo 

Oxygen 0.45  trace 

Nitrogen 7.76  3.28 

Carbon  Monoxide 1.23  0.33 

Carbon  Dioxide 0.90  0.44 

Ethylene  Series o.oo  0.67 

Marsh  Gas 89.66  95.28 

Kiln  Lining. 

The  rotary  kiln  as  has  been  said  is  lined  with  fire  brick.  This 
brick  should  be  of  the  most  refractory  kind.  I  believe  at  one  time 
a  magnesia  brick  was  used  but  now  a  good  quality  fire  brick  is 
considered  as  satisfactory  and  more  economical  than  the  expen- 
sive magnesia  lining.  A  good  fire  brick  should  analyze  within 
these  limits : — 

Per  cent.        Per  cent. 

Silica,  SiO2 • 45.0     to     50.0 

Alumina,  A12O3 43.0     to     48.0 

Iron,  Fe.;O3  '• Less  than    3.0 

Magnesia,  MgO "         "      0.5 

Lime,  CaO "         "      0.5 

It  should  also  be  free  from  iron  and  alkalies,  since  these  cause 
fusibility.  A  fire  brick  lining  should  last,  if  carefully  attended  to, 
at  least  9-12  months  and  sometimes  they  go  even  longer  than  this. 

1  Mineral  Resources  of  Kansas  for  1897. 


122  PORTLAND  CEMENT 

At  the  end  of  this  time  the  bricks  are  eaten  away  nearly  to  the 
iron  shell  and  it  becomes  necessary  to  take  away  the  brick  from 
the  first  20  or  30  feet  of  the  kiln  and  reline  this  portion.  The 
upper  part  of  the  kiln  lining,  or  that  portion  of  it  which  merely 
comes  in  contact  with  the  powdered  raw  material  before  sinter- 
ing commences,  usually  lasts  indefinitely.  In  kilns  working 
on  wet  materials  it  is  sometimes  the  practice  to  leave  the  upper 
20  or  25  feet  of  the  kiln  unlined  since  this  part  of  the  kiln  is  kept 
fairly  cool  by  the  wet  slurry.  Sometimes  channel  irons  or  z  bars 
are  fastened  to  the  sides  of  the  kiln  to  form  shelves  for  drying 
the  material. 

In  place  of  fire  brick  a  concrete  or  clinker  brick  made  from 
Portland  cement  clinker  and  Portland  cement  is  used.  The  clink- 
er should  be  screened  and  that  portion  of  it  passing  a  Y^  inch 
screen  used.  This  is  mixed  with  Portland  cement  in  the  propor- 
tions of  thirty  parts  clinker  to  twelve  parts  cement  and  made 
into  a  medium  wet  concrete.  This  is  then  rammed  into  wooden 
forms  of  the  proper  size  and  shape  and  allowed  to  harden.  The 
bricks  are  ready  for  use  several  days  after  making.  One  large 
mill  in  the  Lehigh  District  used  these  bricks  exclusively  at  one 
time  for  lining  the  clinkering  zone  of  their  kilns,  and  found  them 
very  satisfactory.  Under  conditions  in  this  region,  however,  they 
do  not  seem  to  be  any  cheaper  than  fire  brick. 

The  fire  bricks  used  to  line  the  lower  end  of  the  kiln  are  usually 
from  9  to  12  inches  thick,  and  those  for  lining  the  upper  end,  from 
4  to  6  inches.  These  bricks  are  keyed  to  fit  the  circle  of  the  kiln. 

It  is  sometimes  the  practice  to  place  a  lining  of  sheet  asbestos 
between  the  fire  brick  lining  and  the  steel  shell.  This  protects  the 
tires,  and  also  the  shell,  to  some  extent,  as  it  cuts  off  some  of  the 
heat  transmitted  to  the  latter.  The  writer  has  used  an  asbestos 
lining  several  times  and  found  that  it  unquestionably  cuts  off  some 
heat  from  the  shell.  In  lining  the  kiln  with  asbestos,  l/^  inch 
board  is  usually  used. 

In  the  old  upright  kilns  it  was  the  usual  practice  to  coat  the  lin- 
ing of  the  kiln  with  a  "grout"  of  slurry,  so  that  it  was  natural  for 
something  of  the  same  sort  to  be  tried  upon  the  rotary  kiln.  It 
was  soon  found  that  a  certain  amount  of  the  raw  material  could 


KILNS  AND  BURNING  123 

be  made  to  adhere  to  the  fire  brick  lining  of  the  kiln,  thereby  re- 
moving the  bricks  from  the  scorriiying  action  of  the  caustic  clink- 
er. It  is*  now  the  practice  to  burn  entirely  on  coated  bricks.  When 
this  coating  falls  off,  usually  only  in  patches,  the  kiln  is  heated 
up,  raw  material  is  scraped  down  over  the  bare  spot  and  pounded 
into  place  with  a  heavy  iron  bar.  Water  is  then  usually  run  on 
the  "patch"  to  harden  it.  In  some  mills  salt  is  used  on  the  bare 
spot,  as  it  is  supposed  to  make  the  patch  hold  better.  The  writer 
has  never  seen  any  advantage  in  its  use,  however. 

The  fire  brick  are  held  in  the  kiln  by  a  heavy  angle  iron  run- 
ning around  both  ends  of  the  kiln.  This  also  helps  to  stiffen  the 
kiln  shell. 

The  operation  of  Portland  cement  burning  is  essentially  a  skill- 
ed process  and  a  skilled  workman  is  required  to  attencf  it.  He 
must  know  just  how  the  clinker  should  be  burned  and  have  a  good 
eye  for  "heat,"  so  that  he  can  tell  when  his  kilns  are  hot  enough 
to  clinker  the  raw  material  properly.  The  placing  of  the  patches 
and  the  coating  of  a  freshly  lined  kiln  also  require  some  skill.  To 
be  economically  run  the  kilns  should  be  kept  at  as  nearly  a  uni- 
form temperature  as  the  irregularity  of  the  feeding  devise  will 
permit.  Kilns  run  spasmodically,  first  hot,  then  cold,  require 
much  coal,  turn  out  poorly  burned  clinker,  and  require  much 
patching.  Since  patching  requires  the  stopping  of  the  kiln  the 
output  is  also  cut  down. 

The  burner  should  also  be  a  sufficiently  good  mechanic  to  look 
after  the  mechanical  part  of  his  kilns.  One  burner  usually  looks 
after  two  kilns.  The  operations  of  the  interior  of  the  kiln  are 
watched  through  darkened  glasses.  No  efforts  have  been  made 
to  use  pyrometers  since  the  temperature  must  change  with  the 
refractoriness  of  the  material  and  the  heat  is  entirely  judged  by 
the  incandescence  of  the  interior  of  the  kiln  and  the  clinker  as 
observed  through  these  glasses. 

X  Chemical  Changes  Undergone  in  Burning. 

The  changes  undergone  during  burning  may  be  summed  up  as 
follows : 

The  carbon  dioxide,  existing  in  the  raw  material  in  combina- 
tion with  the  lime  and  magnesia  as  carbonate  of  these  elements, 


124  PORTLAND  CEMENT 

is  practically  entirely  expelled.  Even  the  little  which  exists  in 
freshly  ground,  well  burned  cement  is  probably  most  of  it  ab- 
sorbed from  the  air,  since  cement  very  rapidly  absorbs  carbon 
dioxide  and  water. 

All  of  the  water  originally  present  whether  free  hygroscopic 
or  combined  is  driven  off  and  the  carbon  and  organic  matter  in  the 
raw  material  are  also  burned  away.  The  iron,  the  greater  part  of 
which  is  usually  present  in  clay  and  cement  rock  in  the  ferrous 
condition,  is  almost  completely  oxidized. 

The  sulphur  whether  present  in  the  raw  material  as  sulphide, 
sulphate  or  in  combination  with  organic  matter  is  much  of  it  ex- 
pelled and  the  remainder  is  usually  all  of  it,  except  a  mere  trace, 
found  present  as  calcium  sulphate.  This  is  to  be  expected  since 
calcium  sulphate  gives  off  its  sulphuric  acid,  when  heated 
with  silica.  Indeed,  I  believe  it  has  been  proposed  to  make 
cement  by  heating  together  a  mixture  of  clay  and  gypsum, 
the  sulphuric  anhydride  driven  off  during  the  process  being 
caught  and  condensed  with  water  and  sold  for  sulphuric  acid. 
It  has  also  been  supposed  that  the  sulphur  of  the  coal  entered  the 
clinker.  This  is  erroneous,  since  the  amount  of  gas  slack  neces- 
sary to  burn  100  Ibs.  of  clinker  will  contain  sufficient  sulphur  to 
make  the  clinker  analyze  at  least  1.5  per  cent.  SO3  if  it  were  all 
absorbed,  while  as  a  matter  of  fact  clinker  seldom  analyzes  any- 
where near  this  amount. 

The  alkalies,  potash  and  soda  are  partly  expelled  in  the  kiln. 
In  experiments  made  by  the  writer,  which  will  be  detailed  below, 
the  losses  of  soda  amounted  to  from  19  to  28  per  cent.,  while  those 
of  potash  ran  from  46  to  52  per  cent.  W.  F.  Hillebrand,  of 
Washington,  D.  C.,  has  applied  for  a  patent  on  a  process  for  con- 
densing these  alkalies,  looking  to  their  utilization  as  fertilizers. 
This  loss  of  alkali  is  also  shown  by  analysis  of  the  deposit  collect- 
ing on  the  walls  of  the  kiln  stack,  a  sample  of  which  contained 

Per  cent. 

Soda  . .    i  .38 

Potash  6.83 

In  a  paper  read  by  the  author  before  the  Association  of  Port- 
land Cement  Manufacturers,  the  results  of  an  experiment  to  de- 


KILNS  AND  BURNING 


125 


termine  the  losses  actually  occurring  in  the  rotary  kiln  were 
given.  This  experiment  consisted  in  sampling  carefully  the  raw 
material  going  into  the  kiln,  the  clinker  coming  out  and  the  coal 
used  for  burning.  The  samples  were  taken  every  3  minutes  for 
5  hours.  The  clinker  was  not  sampled  for  45  minutes  after  the 
first  raw  material  sample  was  taken  and  was  collected  for  45 
minutes  after  the  last  raw  material  sample  was  taken;  the  idea 
being  to  allow  the  material  to  work  through  the  kiln  so  that  the 
clinker  represented  the  burned  raw  material.  The  samples  were 
taken  on  kilns  working  normally,  with  a  steady  feed  and  raw 
material  of  constant  composition.  The  samples  were  then  all 
carefully  analyzed.  Three  separate  tests  were  made,  but  only  one 
set  of  results  is  given  here : 


Raw 
material 
as 
analyzed. 

Clinker 
as 
analyzed. 

Raw 
material 
calculated 
to  a  , 
clinker. 

Clinker 
calculated 
without  its 
HoO,  CO2) 
etc. 

I/oss 
or 
Jgain 

Sio    

I  ^  &A. 

21  06 

2O  47 

1  AT 

TiO 

o  ^2 

-f-oy 

A1  Oo   . 

lA^O 

4   ere 

v-3a 

7  2Q 

u-oo 
6  Q1 

•32 

°3 

1    Tn 

Fe  O 

•Do 

f?*7 

2    ^2 

"•Vo 
2   1A 

•Jr 

?  fifi 

~r39 

1      "T 

-TC2W3 

FeO 

o  88 

*'O* 

^•6^ 

•f-32 

MnO  

o  06 

O  OQ 

CaO  

67  72 

67   Qn 

1   ^Q 

Mo-n    . 

I   Qd. 

uoOo 

2  Q^ 

UO-/^ 
2  Q4 

03.00 

-j-05 
1    re? 

Na  o     

i.yq. 

Q     -J  T 

*«yo 

o  38 

••*rt 

2.97 

n  78 

~ho3 

K  O  •• 

U.0l 

O  72 

O   ^Q 

I    IO 

—09 

P  O    . 

O  22 

Y'py 

O  "XA 

u-oy 

51 

J.  2v_/5 

SO 

w-o4 

•o4 
n  ^8 

B»i 

s  

O  \\ 

OQ-7 

1"'0 

0.30 

—  07 

c  

'-'•OO 

O  7^ 

CO   . 

u-  /o 

HO  

6*  -V4 

v»3^ 

In  the  second  and  third  columns  will  be  found  the  analysis  of 


126  PORTLAND  CEMENT 

the  raw  material  and  clinker  respectively.  In  the  fourth  column 
is  calculated  the  composition  the  raw  material  would  have  after 
clinkering  if  the  only  changes  which  took  place  were  the  oxida- 
tion of  the  ferrous  iron  and  sulphur,  the  burning  off  of  the  car- 
bon and  the  volatilization  of  the  carbon  dioxide  and  water.  The 
fifth  column  gives  the  analysis  of  the  clinker  calculated  to  100% 
without  its  water  and  carbon  dioxide  and  after  its  sulphur  and 
iron  had  all  been  calculated  to  SO3  and  Fe2O3  respectively.  The 
coal  used  for  burning  in  the  experiment  was  Fairmont  gas  coal. 
Analysis  of  Fairmont  Gas  Coal : 

Moisture i-34 

Volatile  and  combustible  matter 34. 1 1 

Fixed  carbon 54-°3 

Ash— SiO2 3-59 

TiO2 0.08 

A1203    1.50 

Fe203 1.91 

MnO 0.03 

CaO 0.75 

MgO 0.03 

Na2O   .. • o.io 

K20 0.16 

P2O5 •••• 0.06 

S03 0-54 

8.75 

Sulphur i-77 

Twenty-nine  pounds  of  this  coal,  the  quantity  generally  consid- 
ered necessary  to  burn  100  pounds  of  clinker,  will  contain : 

Pounds. 

Si02 ••" ^^ 

Ti<V" °-02 

A1203    °-44 

Fe203 °-55 

MnO °-01 

CaO °'22 

MgO 
Na20 
K20 

P205 °'02 

SO3  (total  S  to) •  •  •  J-43 

If  we  compare  these  figures  with  those  in  the  last  column  of 


KlXNS  AND  BURNING  127 

the  table,  we  will  see  that  the  silica,  ferric  oxide  and  alumina 
have  been  increased  by  approximately  one-half  the  coal  ash.  Un- 
doubtedly, in  the  rotary  kiln  much  of  the  ash  is  carried  out  with 
the  gasses  by  the  strong  draft  of  the  kiln.  This  we  would  expect 
when  we  consider  that  the  particles  of  ash  are  of  the  same  vol- 
ume as  the  particles  of  coal,  and  yet  only  one-tenth  their  weight, 
for  when  the  coal  burns  it  leaves  its  ash  in  the  form  of  a  skeleton. 
These  particles  of  ash  are  already  in  motion  and  are  in  the  full 
draft.  The  gases  have  a  velocity  of  at  least  2,000  feet  per  min- 
ute,  which  is  quite  enough  to  carry  the  particles  up  the  chimney. 
It  seems  probable  in  view  of  these  facts  that  what  ash  does  con- 
taminate the  clinker,  comes  from  the  impinging  of  the  flame 
upon  the  material  in  the  kiln.  The  ash  strikes  the  clinker  and 
its  velocity  is  stopped  by  the  impact  and  it  either  falls  among  the 
clinkers  or  it  sticks  to  the  red  hot,  semi-pasty  mass.  It  is  proba- 
ble that  the  coarser  the  coal  the  more  ash  will  contaminate  the 
clinker.  It  is  an  important  point  where  this  ash  falls.  If  it  falls 
before  the  raw  material  begins  to  ball  up,  24  Ibs.  extra  limestone 
should  be  added  to  every  600  Ibs.  of  raw  material  to  take  care  of 
the  ash,  as  in  this  case,  it  would  form  Portland  cement  clinker. 
If,  however,  it  falls  on  the  clinker  after  it  forms  into  balls,  this 
quantity  should  be  very  much  less,  if  any  at  all,  as  its  action  is 
merely  on  the  surface  of  the  clinker  to  form  a  slag  and  not  a  true 
Portland  cement  clinker. 

If  we  recalculate  the  clinker,  taking  into  consideration  the  voli- 
tilizing  of  the  sulphur,  potash  and  soda,  and  adding  one-half  the 
elements  introduced  by  the  coal  ash,  we  would  have  a  clinker 
with  the  following  analysis : 

SiO2 21.09 

TiO2 0.36 

A1203 7.17 

»      Fe2O3 2.62 

MnO 0.09 

CaO 63.99 

MgO 2.95 

Na20 0.39 

K20    0.61 

P2°s 0.35 

S03 0.38 


128  PORTLAND  CEMENT 

Comparison  of  these  figures  with  those  of  the  fifth  column 
shows  them  to  be  very  close  to  our  actual  results. 

Another  point  brought  out  by  these  tests  is  the  loss  of  material, 
as  dust,  etc.,  during  the  pulverizing  and  burning  of  the  raw  mate- 
rial and  clinker.  Allowing  the  losses  shown  for  volatilization  of 
the  soda,  potash,  and  sulphur,  in  the  proportions  shown  in  the 
experiment,  and  adding  one-half  of  the  coal  ash,  100  Ibs.  of  raw 
material  should  make  67.25  Ibs.  of  clinker,  or  565  Ibs.  of  raw 
material  should  make  i  barrel,  or  380  Ibs.  of  clinker.  The  rock 
as  it  comes  from  the  quarry  usually  carries  much  more  moisture 
than  the  analysis  shows,  but  even  taking  an  extreme  of  5%  mois- 
ture, 594  Ibs.  should  make  a  barrel  of  clinker.  Few  manufactur- 
ers use  less  than  610  Ibs.,  showing  a  lost  of  16  Ibs.,  as  dust,  etc., 
barrel  of  clinker  produced. 

The  above  changes  are  simply  those  which  we  can  detect  by 
comparative  chemical  analysis  of  the  raw  material  and  the  clink- 
er. None  of  them  are  sufficient  of  themselves  to  form  Portland 
cement.  All  the  carbon  dioxide  can  be  driven  off  the  raw  mate- 
rial and  still  Portland  cement  clinker  will  not  be  the  result.  For 
this  it  is  necessary  that  the  lime  combine  with  the  silica  and 
the  alumina,  and  in  order  for  this  combination  to  take  place  it  is 
necessary  for  the  material  to  be  heated  to  a  considerably  higher 
temperature  than  that  necessary  to  drive  off  carbon  dioxide.  If 
a  small  sample  of  raw  material  is  heated  to  a  constant  weight  over 
an  ordinary  laboratory  blast  lamp,  very  little,  if  any,  clinkering 
will  take  place,  except,  perhaps,  on  the  under  side  of  the  sample 
next  to  the  crucible,  yet  all  the  carbon  dioxide  will  have  been 
driven  off.  The  various  opinions  as  to  the  constitution  of  Port- 
land cement  clinker  have  been  fully  detailed  in  Chapter  II  on  the 
chemical  composition  of  Portland  cement,  and  it  is  unnecessary 
here  to  repeat  them.  W.  B.  Newberry's  experiment  on  the  var- 
ious stages  of  burning  given  below,  and  E.  D.  Campbell's  re- 
searches as  to  clinkering  temperatures,  also  outlined  further  on, 
have  done  something  to  advance  our  knowledge  of  cement  burn- 
ing. 

Wm.  B.  Newberry's  experiment1  is  of  great  interest  as  tend- 

1  Cement  and  Engineering  News,  Vol.  XII,  No.  5. 


KILNS  AND  BURNING 


129 


ing  to  throw  some  light  on  the  question  of  what  takes  place  dur- 
ing the  passage  of  the  raw  material  through  the  kiln. 

During  a  temporary  shut  down  of  one  of  the  rotaries  at  the 
Dexter  Portland  Cement  Co.,  at  Nazareth,  Pa.,  the  kiln  was  al- 
lowed to  cool  down  without  being  emptied  and  samples  of  the 
charge  were  then  taken  from  every  four  feet  throughout  the 
length  of  the  kiln. 

After  careful  examination  these  samples  were  analyzed,  the  re- 
sults showing  the  changes  which  take  place  in  the  composition 
at  successive  stages  of  the  burning.  The  raw  material  used  was 
cement  rock  without  the  addition  of  any  other  material.  The 
first  sample  was  of  unburned  raw  material  taken  at  the  point  of 
entering  the  kiln  and  the  last  (No.  14)  was  the  finished  clinker 
within  four  feet  of  the  discharge  at  the  lower  end. 

Below  is  given  a  table  of  the  successive  analyses : 


'•         No. 

SiO2. 

Fe  and  Al. 

CaO. 

MgO. 

I,oss  on 
ignition. 

I 

13.70 

6.00 

42.12 

i-97 

35-30 

-            2 

I3.65 

5.58 

41-95 

1.96 

35-04 

3 

14.38 

5-70 

41.63 

1.88 

34.84 

'-       4 

13-55 

6.30 

41.98 

2.12 

5^23.46 

5 

14-33 

6.27 

44.05 

1.65 

32.76 

6 

14.46 

6.36 

44.67 

1.89 

^ 
3O.56 

7 

14.90 

6-55 

46.19 

2.30 

28.38 

8 

16.44 

6-99 

49-25 

2.33 

24-94 

5v  9  i 

^6  10 

17.03 
17-94 

7.80 
8.50 

53-04 
56.20 

2.30 
2-35 

18.44 
13.04 

^/^   ii  i 

18.60 

9.04 

59-oo 

2.70 

8-32 

12 

18.66 

9-75 

62.68 

2.80 

4-34 

13 

19.90 

10.76 

63-38 

2.83 

I.  08 

/VI4 

20.36 

10.78 

63.76 

2.8l 

0.86 

.20 


2-0 


,11. 


Z-2. 


The  samples  were  finely  ground  and  analyzed  after  strongly  ig- 
niting and  dissolving  in  half  strength  hydrochloric  acid. 

"It  will  be  seen  from  this  that  the  process  of  burning  in  the 

5 


I3O  PORTLAND  CEMENT 

rotary  takes  place,  not,  as  has  been  supposed,  in  a  series  of  steps, 
but  in  a  continuous  change,  the  moisture  and  organic  matter  be- 
ginning to  pass  off  as  soon  as  the  raw  material  attains  the  tem- 
perature of  the  upper  end  of  the  rotary,  shown  by  the  change  in 
color  from  blue  gray  to  light  buff  or  cream  color  between  3  and 
4.  The  carbonic  acid  soon  follows;  Nos.  4  and  5  at  16  and  20 
feet  showed  marked  loss.  As  the  carbon  dioxide  burns  off,  the 
proportions  of  the  solid  elements  rise  steadily,  the  greatest  varia- 
tions being  shown  from  8  to  12,  when  the  temperature  passes 
from  a  bright  red  to  a  white  heat.  The  whole  of  the  volatile  mat- 
ter is,  however,  not  driven  off  until  the  clinker  is  completely 
burned  and  about  to  leave  the  kiln,  at  which  point  but  .86%  re- 
mains. 

"Much  of  interest  may  be  deduced  from  these  results. 

"The  physical  change  from  raw  stone  to  clinker  is  shown  by 
the  characteristics  of  the  different  samples  given  below : 

"Nos.  i,  2  and  3,  blue  gray  powder,  changing  to  buff  between 
3  and  4. 

"Nos.  4,  5  and  6,  yellowish  buff  powder  commencing  in  6  to 
ball  up  into  small  lumps. 

"Nos.  7,  8,  9  and  10,  yellow  to  brown  balls  like  marbles;  soft, 
easily  crushed  in  the  fingers,  becoming  darker  and  harder  toward 
10. 

"No.  n,  lumps  quite  hard  and  dark  brown,  traces  of  sinter- 
ing on  surface,  softer  inside. 

"No.  12,  lumps  brown  and  partly  sintered,  beginning  to  lose 
regular  rounded  form,  hard. 

"No.  13,  larger  lumps,  irregular  and  rough,  almost  black.  Very 
noticeable  difference  between  12  and  13,  latter  is  like  brownish 
clinker  and  is  burnt  throughout. 

"No.  14,  smaller  and  more  rounded  lumps,  black,  has  all  the 
appearance  of  finished  clinker,  in  fact  no  further  change  is  seen 
as  it  leaves  the  rotary. 

It  is  to  be  hoped  that  the  experiment  will  be  repeated  and 
microscopic  sections  made  of  the  various  samples  of  clinker.  This 
would  throw  still  more  light  upon  the  question. 

Campbell  made  numerous  experiments  in  burning  mixtures  of 
marl  and  clay  in  varying  proportions  in  a  small  rotary  kiln1 

ij.  Am.  Chem.  Soc.,  XXIV,  248. 


KILNS  AND  BURNING  131 

fitted  with  a  Le  Chatelier  pyrometer  and  observing  the  properties 
of  clinker  formed  at  various  temperatures.  From  these  experi- 
ments he  fixed  the  temperature,  necessary  to  properly  burn  most 
commercial  cements  at  1550°  C  or  2822°  F.,  while  high  limed 
cements  would  require  an  even  greater  temperature.  For  exam- 
ple1 ;  he  found  a  mixture  of  clay  and  marl  in  which  the  ratio  of 
the  silicates  (SiO2  +  A12O3  +  Fe2O3)  was  to  the  lime  (CaO) 
as  100 :  228.8,  and  which  gave  a  clinker  containing  62.64  per 
cent,  lime,  to  require  a  temperature  of  1549°  C.  for  proper  burn- 
ing, while  a  mixture  of  the  same  clay  and  marl  in  which  the  sili- 
cate-lime ratio  was  100 :  240.8  and  which  gave  a  clinker  analyz- 
ing 63.83  required  a  temperature  of  1593°  C.  A  third  mixture  of 
these  materials  having  a  silicate-lime  ratio  of  100:  266.4  and  giv- 
ing a  clinker  analyzing  66.12  per  cent,  lime  failed  to  burn  per- 
fectly even  at  1625°  C. 

This,  of  course,  corroborates  the  experience  of  every  cement 
chemist,  that  the  higher  the  lime,  other  things  being  equal,  the 
higher  temperature  is  needed  to  burn  it. 

In  the  same  series  Campbell  also  found  that  the  mixture  of 
clay  and  marl  with  the  silicate-lime  ratio  of  100 :  228.8,  which 
required  a  temperature  of  1549°  C  for  proper  burning  could  be 
burned  at  a  temperature  of  1478°  C  by  revolving  the  kiln  more 
slowly.  This  again  corroborates  the  experience  of  manufactur- 
ers, that  a  longer  time  in  the  kiln  would  do  the  same  work  as  a 
much  higher  temperature. 

In  a  second  experiment2,  Campbell  and  Ball  investigated  the 
influence  of  fine  grinding  of  the  raw  materials  on  the  clinkering 
of  cement.  A  mixture  of  cement  rock  from  the  Lehigh  District, 
as  ground  ready  for  the  kiln  by  a  prominent  mill  of  this  region, 
was  subjected  to  a  sieve  test  and  found  to  run  72.4  per  cent, 
through  a  2OO-mesh  sieve  and  85.6  per  cent,  through  a  loo-mesh 
sieve.  This  mixture  could  not  be  thoroughly  burned  even  at 
1612°  C.,  but  when  reground  so  that  98  per  cent,  of  it  passed  a 
2OO-mesh  sieve  proper,  burning  was  accomplished  at  a  tempera- 
ture of  1475°  C  or  137°  C  less.  This  experiment  is  valuable  as 
showing  the  importance  of  fine  grinding  in  fuel  economy.  While 

iy  Am.  Chem.Soc.,  XXIV,  969. 
ay.  Am.  Chem.  Soc.,  XXV,  1103. 


132  PORTLAND  CEMENT 

it  would  probably  be  impracticable  to  grind  hard  raw  materials  to 
a  fineness  of  98  per  cent,  through  a  2OO-mesh  sieve,  it  is  practica- 
ble and  indeed  is  usual  to  grind  more  than  85  per  cent,  through  a 
loo-mesh  sieve. 

While  there  is  no  definite  information  to  that  effect  it  is  gen- 
erally accepted  as  a  fact  that  the  presence  of  alkalies  lower  the 
temperature  at  which  clinkering  takes  place.  In  a  small  furnace 
which  the  writer  had  he  could  never  quite  get  the  temperature  up 
to  the  point  for  a  thorough  burning  of  the  Lehigh  cement  rock- 
limestone  mixtures,  but  if  the  small  cubes  of  powdered  mate- 
rial were  made  up  with  water  containing  enough  sodium  carbon- 
ate to  make  the  mixture  analyze  about  1.5  per  cent,  soda,  the 
clinkering  could  easily  be  accomplished. 

Iron  also  plays  an  important  part  in  aiding  the  clinkering. 
Various  experimenters  who  have  endeavored  to  make  white  ce- 
ment by  the  use  of  iron  free  clays  and  marl  or  limestone  have 
found  it  hard  to  clinker  the  material  properly  and  have  gotten 
around  the  difficulty  usually  by  addition  of  alkali  in  the  form  of 
feldspar.  Fluorspar  or  calcium  fluoride,  CaF2,  has  also  the  effect 
of  lowering  the  clinkering  temperature  and  has  been  used,  com- 
mercially, for  that  purpose,  I  believe. 

Degree  of  Burning. 

Properly  burned  Portland  cement  clinker  is  greenish  black  in 
color,  of  a  vitreous  lustre  and  usually  when  just  cooled  sparkling 
with  little  bright  glistening  specks.  It  forms  in  lumps  from  the 
size  of  a  walnut  down,  with  here  and  there  a  larger  lump.  Un- 
derburned  clinker,  whether  this  is  due  to  a  low  temperature  in 
the  kilns  or  an  overlimed,  mixture  lacks  the  vitreous  lustre  and 
the  glistening  specks.  The  failure  to  sparkle,  however,  is  not  nec- 
essarily characteristic  of  underburned  clinker,  though  the  sparkle 
itself  is  never  seen  in  underburned  clinker,  as  the  rate  of  cooling 
etc.,  effects  this  somewhat.  If  much  underburned/ the  clinker  is 
brown,  or  has  soft  brown  or  yellow  centres.  Low  limed  clinker 
unless  very  carefully  burned,  usually  has  brown  centres  also,  but 
is  hard  and  glassy.  The  two  should  not  be  mistaken ;  the  clinker 
with  soft  brown  centres  is  underburned  that  with  hard  brown 
centres  is  underlimed. 


KILNS  AND  BURNING  133 

Overburned  clinker  shows  the  same  characteristic  as  under- 
limed, — the  hard  brown  centres.  I  have  never  seen  that  the  quality 
of  cement  was  injured  any  by  overburning,  unless  the  material 
was  low  in  lime  when  the  resulting  cement  was  apt  to  be  ' 'quick 
setting,"  but  the  proper  degree  of  sintering  is  far  enough  to  carry 
the  process  and  to  burn  any  harder  is  not  only  a  waste  of  coal  for 
burning,  but  also  for  grinding  since  the  hard  brown  slag  like 
clinker  is  very  hard  to  pulverize.  Properly  burned  clinker  should 
have  a  specific  gravity  of  at  least  3.15  and  when  rapidly  pulver- 
ized and  ignited  show  a  loss  of  under  I  per  cent. 

Thermo-Chemistry  of  Burning. 

These  chemical  changes  or  reactions  either  give  off  or  require 
heat.  If  the  former  they  are  exothermic,  if  the  latter  endother- 
mic. 

The  exothermic  or  heat  generating  reactions  are  the  burning  of 
the  sulphur  and  carbon  (organic  matter)  of  the  raw  materials. 
The  endothermic  or  heat  absorbing  ones  are  the  decomposition 
of  the  calcium  and  magnesium  carbonates. 

The  combination  of  the  lime  with  the  silica  and  alumina  is  also 
thought  to  be  an  exothermic  reaction,  but  authorities  differ  on 
this  point. 

The  quantity  of  heat  generated  by  chemical  reaction  or  re- 
quired to  bring  it  about  is  usually  expressed  in  terms  of  one  of 
two  units.  These  are  the  British  Thermal  Unit,  usually  ab- 
breviated to  B.  T.  U.  and  the  Calorie  sometimes  abbreviated 
to  Cal.  The  British  Thermal  unit  is  the  heat  required  to 
raise  the  temperature  of  one  pound  of  pure  water  through 
one  degree  Fahrenheit  at  or  near  39.1°  F.,  the  tempera- 
ture of  its  maximum  density.  The  Calorie  is  the  heat 
necessary  to  raise  the  temperature  of  one  kilogram  of 
water  from  4°  C.  to  5°_C,  A  calorie  is  equivalent  to  3,968  B.  T. 
U.,  and  a  B.  T.  U.  to  0.252  Calorie.  The  B.  T.  U.,  however,  pro- 
duced by  the  oxidation  or  combustion  of  one  pound  of  a  sub- 
stance is  9/5  of  the  number  of  Calories  which  would  be  produced 
by  one  kilogram  of  the  substance.  Hence,  to  reduce  Calories  per 


134  PORTLAND  CEMENT 

kilogram  to  B.  T.  U.  per  pound  multiply  by  9/5  while  to  change 
B.  T.  U.  per  pound  to  Calories  per  kilogram  multiply  by  5/9. 

The  British  Thermal  Unit  is  the  one  generally  used  by  engi- 
neers for  expressing  the  heating  value  of  fuel  while  the  calorie  is 
used  in  most  scientific  calculations. 

The  following  are  the  heat  values  of  the  reactions  mentioned 
above : 

B.  T.  u. 

i  pound  of  carbon  burned  to  CO2  gives  off 14*540 

i  pound  of  sulphur  burned  to  SO2  gives  off 4,050 

i  pound  of  CaCO3  decomposed  into  CO2  and  CaO  requires      784 l 
i  pound  of  MgCO3  decomposed  into  CO2  and  MgO  re- 
quires        384 1 

i  pound  of  CaO  uniting  with  SiO2  and  A12O3  gives  off. .     1064  l 
0.56  pound  of  CaO,  equivalent  to  i  pound  of  CaCO3  unit- 
ing with  SiO2  and  A12O3,  gives  off 596 l 

Calories. 

I  kilogram  of  carbon  burned  to  CO2  gives  off 8,080 

i  kilogram  of  sulphur  burned  to  SO2  gives  off 2,250 

i  kilogram  of  CaCO3  decomposed  into  CO2  and  CaO  re- 
quires    436 1 

i  kilogram  of  MgCO3  decomposed  into  CO2  and  MgO  re- 
quires    213 l 

i  kilogram  of  CaO  uniting  with  SiO2  and  A12O3  gives  off  591 l 
0.56  kilogram  of  CaO,  equivalent  to  i  kilogram  of  CaCO3. 

uniting  with  SiO2  and  A12O3  gives  off 331  * 

As  I  have  said  there  is  some  doubt  about  the  heat  given  off  by 
the  combination  of  the  lime  with  the  silicates,  and  this  point  needs 
investigation.  It  is  the  one  stumbling  block  to  our  calculating  the 
efficiency  of  the  rotary  kiln.  As  it  seems  probable  that  the  reac- 
tion does  give  off  some  heat,  though  the  amount  is  probably  very 
small,  we  can  arrive  at  the  maximum  heat  theoretically  required 
to  burn  a  barrel  of  cement,  or  rather  the  heat  from  outside 
sources  absorbed  by  the  chemical  reactions. 

As  we  have  said  heat  is  required  to  decompose  the  carbonates 
and  is  given  off  by  the  burning  of  the  carbon  and  the  sulphur  of 
the  mix1.  The  raw  material  of  the  Lehigh  District  contains  per 
100  pounds,  about 

1  Berthelot,  Thermochemie,  Vol.  II.     These  values  are  dubious. 

2  If  the  sulphur  of  the  mixture  is  present  as  sulphide,  it  burns,  giving  off  heat.     If 
present  as  sulphate,  heat  is  required  to  expell  it  (1890  B.  T.  U.  per  pound.) 


KILNS  AND  BURNING  135 

Pounds. 

Carbonate  of  lime 75.0 

"  "  magnesia 4.0 

Carbon 0.8 

Sulphur 0.3 

Hence,  there  would  be  required  heat  as  follows : 

B.  T.  u.        B.  T.  u. 

To  decompose  75  Ibs.  of  CaCO3  =  75  X  784 58,800 

To  decompose  4  IDS.  of  MgCO3  =  4  X  384 i  ,536        60,336 

There  would  be  given  off : 

By  burning  of  0.3  Ibs.  of  sulphur  =0.3  X  4050- .1,2 15 

By  burning  of  0.8  Ibs,  of  carbon  0.8  X  14,540.  .11,632         12,847 

Balance  to  be  supplied  by  fuel 47,489 

Since  I  barrel  of  cement  requires  about  600  Ibs.  of  dry  material 
it  would  require  47,489  X  6  B.  T.  U.,  or  reckoning  I  Ib.  of  Fair- 
mont gas  slack  at  14,000  B.  T.  U.,  i  barrel  of  cement  would  re- 

47,489  X  6  11  r 

quire  -  -  or  20.35  "*.  of  coal. 

14,000 

If  we  consider,  however,  that  heat  is  given  off  by  the  combina- 
tion of  the  lime  with  the  silicates,  then  this  heat  would  amount  to 
75  X  596  =  44,700  B.  T.  U.  Subtracting  this  from  47,489  would 

leave  only  2,780  B.  T.  U.  to  be  supplied  by  the  coal  or  

14,000 

=  1.2  Ibs.  of  coal  per  barrel.  This  latter  figure  seems  hardly 
probable. 

Of  course,  the  figure  20.35  ^s-  °f  coa^  Per  barrel  is  an  ideal 
one,  and  in  order  to  realize  it  in  practice  we  would  have  to  re- 
cover all  the  heat  not  actually  utilized  in  the  chemical  reaction. 
We  would  have  to  cut  off  all  radiation  from  the  kiln,  the  clinker 
and  flue  gases  would  have  to  leave  the  kiln  at  the  temperature  of 
the  air,  and  we  would  have  to  condense  the  water  evaporated 
from  the  mix  and  recover  the  heat  units  expended  upon  it. 

Of  course,  it  is  impossible  to  do  this  economically.  There  will 
always  be  some  loss  by  radiation,  and  the  water  must  leave  the 
kiln  at  a  temperature  above  its  boiling  point.  We  must  also  have 
sufficient  difference  between  the  temperatures  of  the  waste  gases 
and  the  outside  air  to  produce  natural  draft.  Table  XVIII  shows 
the  various  constants  necessary  to  calculate  the  heat  carried  off 
by  the  kiln  gases  and  the  clinker. 


136  PORTLAND  CEMENT 

TABLE  XVIII.— CONSTANTS1,  ETC.,  FOR   USE  IN  CALCULATING 
THE  HEAT  LOSSES  OF  THE  ROTARY  KILN. 

Pounds 
Weight  of  air  necessary  to  burn  one  pound  of — 

Carbon  (to  CO2) n.6 

Hydrogen  (to  H2O) 34.8 

Sulphur  (to  SO2 ) 4-4 

Weight  of  products  of  combustion  from  one  pound  of— 

Carbon CO2  =  3.66  Ibs.     N  =    8.94  Ibs. 

Hydrogen H2O  =  9.00  Ibs.     N  =  26.8    Ibs. 

Sulphur SO3  =  2.oolbs.     N=   3.35  Ibs. 

B.  T.  u. 

Heat  required  to  evaporate  i  Ib.  of  water 996 

Specific   heat  of  products  of  combustion  of  i  Ib.  of  gas 

slack  coal 0.250 

Specific  heat  carbon  dioxide 0.234 

"  ' '     carbon  monoxide o.  245 

"  "     nitrogen 0.244 

"     air 0.238 

"  "     steam 0.480 

"  "     water i.ooo 

"  "     clinker 0.246 

Below  is  an  analysis  of  Fairmont  gas  slack  coal  ( such  as  is  used 
in  the  Lehigh  District)  made  by  the  writer: 

Water  (iio°C.) 1.9 

Carbon 74.9 

Hydrogen 4.8 

Oxygen 8.6 

Nitrogen 1.4 

Sulphur o.  7 

Ash 7.7 


1 00.0 

Neglecting  the  sulphur  which  is  present  only  in  very  small 
amount  the  combustible  elements  in  100  Ibs.  of  this  coal  are  74.9 
Ibs.  of  carbon  and  4.8  Ibs.  of  hydrogen.  Of  this  hydrogen,  how- 

O      £ 

ever,  -  -  Ibs.  will  be  needed  for  the  oxygen  of  the  coal  itself, 
8 

Q    f-\ 

leaving  only  (4.8  —      —  =  4.8  —  i.i  =  3.7)    to   require    outside 
8 

oxygen ;  hence,  to  burn  100  Ibs.  of  this  coal  will  require 

1  These  constants  are  of  course  mere  approximations,butare  sufficiently  near  the  truth 
for  rapid  calculations  of  heat  losses. 


KILNS  AND  BURNING  137 

For  the  carbon 74.9  X  11.6  =  869  Ibs.  air 

For  the  hydrogen 3  7  X  34-8==  129  "     " 

Total  for  100  Ibs.  coal =998"     " 

Total  for  i  Ib.  coal  . =  10.0  "     " 

The  products  of  combustion  from  100  Ibs.  of  coal  would  of 
course  weigh  998  Ibs.  +  combustible  and  volatile  part  of  the  coal 
or  998  +  ( IO°  —  asn)  • 

Therefore,  products  of  combustion  from  100  Ibs.  of  coal  would 
weigh  998+  (100  —  7.7)  =  1090  and  products  of  combustion 
from  one  pound  of  coal  10.9  Ibs. 

Now  neglecting  the  unimportant  elements : — 

The  combustion  of  74.8  Ibs  of  car- 
bon will  produce  :  74  8  X  3-66  =  274  Ibs.  of  CO2. 

And  74.8X8.94  =  669         "     N. 

The  combustion  of  3.7  Ibs.  of  Hy- 
drogen will  produce  :  3-7X9       =33         "     H2O. 

And  3.7  X  26.8=    99         "     N. 

Now  there  are  1.9  Ibs.  of  water  from  the  moisture  of  the  coal 

Q        £ 

and  8. 6  H — '- —  =  9.7   Ibs.   from   the  oxygen  of  the   coal,   hence 

8 

there  will  be  in  the  products  of  combustion  from  100  Ibs.  of  coal 
768  Ibs.  of  nitrogen,  274  Ibs.  of  carbon  dioxide,  and  44.6  Ibs.  of 
water. 

Hence,  the  mean  specific  heat  of  the  gases  will  then  be  :— 

Nitrogen 768  X  .244  =  187.4 

Carbon  dioxide 274  X  .234  =•    64.1 

Water  (steam) 45  X  .48    •=    21.6 

1087  273.1 

27  T,    I 

Mean  specific  heat  =  — -^ o. 25 1 . 

This  figure  may  be  taken  as  fairly  representative  of  the  specific 
heat  of  the  products  of  combustion  from  gas  slack  coal.  It  is  of 
course  not  a  very  exact  figure  because  the  specific  heat  of  gases 
increases  slightly  with  their  temperature.  It  is  probably  exact 
enough  for  ordinary  purposes,  however,  since  in  most  calculations 
of  this  sort  so  much  is  assumed  that  very  exact  figures  are  merely 
a  waste  of  mathematics. 


138  PORTLAND  CEMENT 

Numerous  tests  of  the  waste  gases  of  the  rotary  kiln  working 
on  dry  material  under  normal  conditions  show  a  temperature  at 
the  mouth  of  the  kiln  of  from  1500°  F.  to  2200°  F.  Analysis  of 
these  gases  also  show  some  excess  of  air,  not  so  much  as  some- 
times stated,  but  still  from  15  to  30  per  cent.  From  his  exper- 
ience, the  writer  would  say  that  the  average  temperature  of  the 
flue  gases,  taken  from  the  kiln  mouth  before  being  diluted  with 
the  air  leaking  into  the  stack,  is  at  least  1950°  F.,  and  that  the 
excess  air  is  20  per  cent,  of  that  actually  required.  The  average 
coal  consumed  is  100  Ibs.  per  barrel  (not  counting  coal  used  to 
heat  up  kiln  after  patching,  etc.,)  and  the  average  weight  of  CO2 
driven  off  per  barrel  is  200  Ibs. 

Then  using  data,  in  Table  XVIII,  the  heat  lost  up  the  stack  is : 

B.  T.  U. 

per  degree  B.  T.    U. 

above  temp.  in  gases, 

of  atmosphere. 

In  products  of  combustion  of  100  Ibs.  of  coal 

=  loo  X  10.9  X  -251  = 273.6 

In     CO2    driven    off    from     raw     material 

=    200  X  0-234  = 46.8 

In      excess      air      used      to      burn       coal 

=   100  X  JO.OX  0.20X0.238 ••  47.6      >     |^rf     i         ^0,£i»0 

368.0 

If  the  outside  air  is  50°  F.  thejgases  would 

contain  368.0  X  (1950 —  50)  — 700,150 

If  raw  material  contains  1%   mois-  ] 
ture,  to  raise  600  X  0.02  or  12  Ibs. 
of  water   from  50°  to  212°  F.  re- 
quires 12  X  (212  —  50)  = 1,944 

To  evaporate   12  Ibs.   of  water  re- 
quires 12X966= n,592 

To  raise   12  Ibs.  steam  from  212  to 

1950=  (1950  —  212)  X  12X0.48-    io,oii  J 

Total  heat  lost  in  waste  gases 723,697 

Since   i  Ib.  coal  =14,000  B.   T.  U.,  heat  lost  up  stack  is  equivalent  to 

723,697  -T-  14000  =  51.7  pounds  of  coal. 

Also  380  Ibs.  of  clinker  at  2160°  F.  (usual  temperature  of  clinker  leaving 

the  kiln)    will  contain   380  X  (  2160  —  50  )  X  o.  246  =  197,243   B.  T.   U.  or 

197^243  _          pounds  of  coal. 
14,000 

Total  heat  carried  off  by  the  waste  gases  and  clinker  is  therefore  equiva- 
lent to  65.8  pounds  of  coal  or  65.8  per  cent,  of  fuel. 


23,547 


KILNS  AND  BURNING  139 

The  above  conditions  are  not  exaggerated,  but  are  a  fair  ex- 
ample of  conditions  as  they  are  usually  met  with  in  burning  dry 
material. 

It  is  interesting  to  note  to  what  figure  ideal  practice  would  re- 
duce the  coal  consumption.  If  the  kiln  gases  are  reduced  to  450° 
F.,  it  will  be  no  better  than  ordinary  boiler  practice  in  many  pow- 
er plants.  The  excess  air  is  now  as  low  as  20  per  cent.  It  would 
also  be  possible  to  reduce  the  temperature  of  the  clinker  to  150° 
F.,  or  even  lower.  Under  these  conditions  let  X  =  coal  con- 
sumed : 

Then  as  before  heat  carried  off: 

B.  T.  U.  per 
degree  above  tem- 
perature of  atmosphere 

In  products  of  combustion  X  X  i°-9  X  0-251  — 2.74^ 

In  CO2  from  raw  material 46.8 

In  excess  air  X  X  IO-°  X  0.20  X  0-238 . 0.48^" 

Total  =  (2.74X  +  0.48  X  +  46.8)  400  =  (3.22  X  + 

46.8)  400  = 1288  X+ 18720 

To  raise  12  Ibs.  water  from  50-2 12°F  and  evaporate  same 

=*   13536 

To  raise  12  Ibs.  steam  from  212-450  —  (450 — 2i2)X  12  X 

0.48 1371 

Total  to  evaporate  water I4»9°7  B.  T.  U. 

Total  heat  in  products  of  combustion,   1288  X  -\-  18720 

4-   14,907  = 1288  X  -f  33-627  B.  T.  U. 

Now  the  clinker  will  carry  off  at  150°  F.  380  X  (150  —  50) 

X  0.246  =  9348  B.  T.  U. 
The  chemical  reaction  will  require  as  calculated  47,489 

X  6 —  284,934  B.  T.  U. 
Or   the  whole  process   will    require   1288^-1-33,627-)- 

9,348  +  284,934  B.  T.  U. 

Or  since  coal  gives  off  14,000  B.  T.  U.  we  have  the  equa- 
tion, 1288  X  -f  33,627  -f  9,348  -f  284,934  =  14000  X. 
Or  327,909  —  12,712^. 

^=25.8  pounds. 

Therefore,  we  should  hope  to  burn  cement  ultimately  with  30 
Ibs.  of  coal  per  barrel.  Of  course  the  value  of  coal  depends  large- 
ly upon  the  heat  units  it  contains  and  40  per  cent,  more  of  a  coal 
giving  off  only  10,000  heat  units  will  be  required. 

Excess  Air  Used  in  Burning. 

The  excess  of  air  admitted  to  the  kiln  over  and  above  that  re- 
quired to  consume  the  coal  has  been  variously  stated  at  from 


I4O  PORTLAND  CEMENT 

loo  to  150  per  cent,  above  the  theoretical  quantity.  From  the  re- 
sult of  many  analyses  made  by  myself  and  friends  I  am  confident 
that  this  does  not  represent  normal  conditions.  If  the  sample  is 
taken  from  the  kiln  stack  a  large  quantity  of  air,  which  has  leak- 
ed in  through  the  annular  opening  between  the  kiln  and  the  brick- 
work of  the  flue  is  sure  to  be  present,  and  consequently  make  the 
excess  air  appear  much  greater  than  it  really  is.  The  gas  sam- 
ples should  be  taken  from  inside  the  mouth  of  the  kiln  so  that 
there  is  no  air  mixed  with  it  which  does  not  pass  through  the 
kiln.  Below  are  given  some  average  analyses  of  waste  gases 
from  kilns  working  under  various  conditions. 

I.  Average  of  all  samples  taken  when  the  kiln  was  working 
normally.  No  flame  or  black  smoke  issuing  from  the  kiln  stack 
but  only  a  thin  white  or  reddish  vapor. 

Carbon  Dioxide 27.4 

Carbon  Monoxide 0.3 

Oxygen 2.7 

Nitrogen 69.6 


100.0 

2.  Average  of  all  samples  taken  when  the  kiln  stacks  were 
smoking. 

Carbon  Dioxide 19.2 

Carbon  Monoxide 1.2 

Oxygen 3.4 

Nitrogen 76.2 


i  oo.o 
3.  Average  of  all  samples  taken  when  kiln  stacks  were  flaming: 

Carbon  Dioxide 14.2 

Carbon  Monoxide 5.8 

Oxygen i.i 

Nitrogen 78.9 


100. 0 

The  nitrogen  in  the  gases  represents  the  air  admitted  for  com- 
bustion as  practically  all  of  it  is  from  either  the  excess  air  or  the 
air  actually  used  to  burn  the  coal.  A  small  part  of  the  nitrogen 
comes  from  the  coal,  however,  but  for  practical  calculations  the 
nitrogen  may  be  considered  as  all  coming  from  the  air.  The  ex- 


KII^NS  AND  BURNING  14.! 

cess  air  is  shown  by  the  oxygen.  If  we  calculate  the  nitrogen 
equivalent  to  this  oxygen  by  multiplying  the  percentage  of  the 
latter  by  3.78,  the  result  will  be  the  nitrogen  carried  in  by  the  ex- 
cess air  and  this  nitrogen  subtracted  from  the  total  percentage  of 
nitrogen  found  by  the  analysis  will  give  the  nitrogen  belonging 
to  the  air  needed  to  support  combustion,  from  which  data  the 
excess  can  be  calculated.  For  example,  to  find  excess  air  in 
sample : 
Analysis  No.  i. 

Per  cent. 

Total  nitrogen 69.6 

Nitrogen  in  excess  air  2.7  X  3.78 10.2 

Nitrogen  in  necessary  air 59.4 

Ratio  :  59.4  :  69.4  :  :  100  :  x 

x  —  117. 
Excess  =  17%  of  air  necessary  to  combustion. 

The  above  calculation  is  not  strictly  accurate  for  a  number  of 
reasons,  but  for  practical  use  it  answers  the  purpose  as  well 
since  we  never  know  in  mill  practice  under  present  conditions 
exactly  how  much  coal  we  are  burning,  or  how  much  carbon 
dioxide  is  being  driven  off  at  a  given  time  from  the  raw  mate- 
rial. 

Of  the  air  admitted  to  the  kiln  for  combustion,  between  20  and 
30  per  cent,  is  blown  in  with  the  coal ;  the  rest  enters  between  the 
hood  and  the  kiln  and  where  the  clinker  drops  out,  and  is  drawn 
in  by  the  draft  of  the  kiln. 

Utilization  of  Waste  Heat. 

Many  ways  have  been  proposed  for  saving  the  waste  heat  from 
the  rotary  kiln,  both  in  the  flue  gases  and  the  clinker. 

Robert  F.  Wentz  and  Lathbury  and  Spackman  both  patented 
clinker  cooling  devices  on  the  principle  of  blowing  air  through 
the  clinker  and  using  the  same  for  combustion  of  the  coal,  and 
each  firm  has  installed  their  system  in  the  mills  which  they  de- 
signed. Rotary  coolers  are  also  in  use  in  a  large  number  of 
works,  but  as  we  have  said  the  majority  of  mills  use  the  large 
upright  coolers  mentioned  in  the  section  on  cooling  the  clinkers 
and  no  attempt  is  made  to  save  the  heat  of  the  clinker  in  spite  of 
the  fact  that  the  heat  in  the  clinker  represents  that  from  the  com- 


142  PORTLAND  CEMENT 

bustion  of  14  Ibs.  of  coal.  There  should  be  no  mechanical  trouble 
about  designing  a  cooler  to  economize  this  heat,  and  yet  cool  the 
clinker.  In  some  of  the  regenerative  systems  the  writer  believes 
failure  to  have  resulted  simply  from  the  fact  that  the  designers 
did  not  realize  that  one  cubic  foot  of  air  at  600°  F.  would  not 
burn  as  much  coal  as  one  cubic  foot  of  air  at  60°  F.,  but  only 
about  half  as  much,  and  consequent  use  of  too  small  a  fan  to  draw 
the  air  through  the  cooler.  The  use  of  the  heat  of  the  clinker  to 
heat  the  water  for  the  boilers  should  also  prove  an  easy  problem. 

In  the  early  days  of  the  rotary  kiln  Giron,  Nivarro,  Hurry  and 
others  patented  devices  for  utilizing  the  heat  of  the  waste  gases. 

At  the  present  time  two  methods  are  being  experimented  with 
for  the  saving  of  the  heat  in  the  kiln  gases. 

( i ) .  Lengthening  the  kiln,  thereby  giving  greater  time  for  the 
material  to  absorb  the  heat  of  the  kiln  gases. 

(2).  Passing  the  gases  of  the  ordinary  short  kiln  through  an 
upright  boiler  and  then  through  an  economizer. 

Thomas  A.  Edison  is  the  chief  exponent  of  the  long  kiln,  as 
those  in  his  plant  at  Stewartsville  are  150  feet  long.  He  was  the 
first  person  in  this  country  to  attempt  such  a  long  kiln. 

These  kilns  were  put  in  operation  in  the  fall  of  1903  and  proved 
entirely  practical  and  effected  the  economy  in  fuel  which  Edison 
had  promised  they  would  do.  His  experiment  was  watched 
with  great  interest,  and,  as  soon  as  the  success  of  these  mammoth 
kilns  was  known,  several  of  the  mills  then  under  construction 
lengthened  their  kilns  to  80  feet.  This  plan  has  also  been  tried 
by  some  of  the  older  mills  who  extended  their  kilns  to  80  or  100 
feet.  Several  of  the  mills  now  being  built  are  erecting  TOO  and 
125-foot  kilns. 

Detailed  information  as  to  the  actual  economy  of  the  long  kilns 
is  hard  to  secure.  From  my  own  observation  and  tests  of  the 
150  foot  kiln  I  should  place  their  output  at  750  barrels  per  day 
with  a  coal  consumption  of  85  Ibs.  per  barrel.  From  the  most  re- 
liable data  available  the  80  foot  kilns  on  dry  material  should  turn 
out  300  barrels  per  day  with  a  coal  consumption  of  90-95  Ibs.,  and 
the  100  foot  kilns  should  turn  out  400  barrels  per  day  with  a  coal 
consumption  of  85-90  Ibs.  per  barrel.  The  long  kiln,  100  feet, 


KILNS  AND  BURNING  143 

working  on  wet  materials,  has  reduced  the  coal  consumption  to 
about  no  Ibs.  per  barrel  with  an  output  of  about  150  barrels  per 
day.  In  the  Great  Northern  Portland  Cement  Co.  the  equivalent 
of  a  kiln  120  feet  in  length  is  used,  the  upper  60  foot  portion 
being  for  mechanical  reasons  separated  from  the  lower  part,  and 
arranged  so  that  it  can  receive  the  waste  heat  from  the  boilers 
and  from  an  additional  fire  underneath  the  drier  when  desired. 
The  results  showed  a  decided  increase  in  quantity  and  an  im- 
provement in  economy,  as  compared  with  those  usually  obtained 
in  burning  materials  containing  the  same  amount  of  water. 

'  Quite  a  number  of  mills  working  on  wet  materials  have  used 
similar  separate  driers  through  which  the  kiln  gases  are  passed. 

The  output  of  a  kiln  is  not  only  dependent  upon  the  length  but 
also  upon  the  diameter.  Eighty  and  100  ft.  kilns  are  usually  made 
7  ft.  in  diameter.  The  greater  the  diameter  the  greater  the  out- 
put of  the  kiln,  but  the  greater  also  its  coal  consumption  per  bar- 
rel. 

Edison's  150  foot  kilns  are  9  feet  in  diameter  and  each  kiln  con- 
sists of  a  series  of  cast  iron  cylindrical  shells  bolted  together  and 
lined  with  fire  brick.  They  are  driven  at  a  point  toward  the  cen- 
ter by  a  25-horse-power  motor  with  speed  reduction  gears  mesh- 
ing with  a  large  spur  gear  around  the  kiln.  The  kiln  is  supported 
at  an  angle  of  2,^/2  degrees  with  the  horizontal  by  means  of  thirty 
supporting  wheels  and  the  thrust;  owing  to  its  inclined  position, 
it  is  taken  up  by  two  auxiliary  wheels  bearing  against  collars,  as 
shown.  Ordinarily  the  kilns  are  rotated  at  a  speed  of  i  turn  per 
minute  and  the  material  in  passage  through  it  takes  about  il/2 
hours.  At  the  discharge  end  it  falls  into  a  secondary  revolving 
cylinder  which  is  furnished  to  serve  as  a  clinker  cooler  and  a 
regenerator,  in  that  the  air  passed  upward  through  the  auxiliary 
cylinder  is  finally  admitted  into  the  kiln.  Pulverized  coal  is  em- 
ployed, as  usual,  for  combustion,  but  forced  in  by  means  of  com- 
pressed air.  Owing  to  the  extreme  length  of  the  kiln,  two  coal 
jets  are  employed,  one  with  air  at  a  higher  pressure  than  the 
other  to  throw  the  coal  jet  as  great  a  distance  as  possible. 

The  attempt  to  utilize  the  heat  of  the  kiln  gases  under  boilers 
was  first  made,  I  believe,  at  the  plant  of  the  Nazareth  Portland 
Cement  Co.,  but  after  encountering  many  difficulties,  the  plan 


144  PORTLAND  CEMENT 

was  abandoned  and  the  boilers  taken  away.  Prof.  R.  C.  Car- 
penter, of  Cornell  University,  however,  has  successfully  tried  this 
plan  at  the  plant  of  the  Cayuga  Lake  Cement  Co. 

The  works  referred  to  have  a  small  plant  consisting  of  four 
kilns  and  grinding  machinery  sufficient  for  about  600  barrels  per 
day,  which  is  located  on  the  shores  of  Cayuga  Lake,  about  six 
miles  north  of  Ithaca,  N.  Y.  In  this  plant  one  boiler,  of  the  ver- 
tical water-tube  type,  as  built  by  the  Wickes  Bros.  Mfg.  Co.,  and 
of  3,000  square  feet  of  water  heating  surface,  was  installed  for 
each  two  kilns  of  the  plant.  After  two  kilns,  composing  one- 
half  of  the  plant,  had  been  in  operation  about  two  months,  a  test 
was  made  to  determine  the  economy  of  the  plant  and  also  the 
amount  of  steam  obtained  from  the  waste  gases. 

Prof.  Carpenter1  gives  the  following  description  of  the  test  and 
its  results. 

At  the  time  of  the  test  two  kilns  only  were  in  operation  and 
the  waste  heat  from  these  kilns  passed  through  one  boiler;  the 
other  boiler  when  used  being  fired  by  hand  exclusively.  The  tests 
of  the  two  boilers  were  made  on  different  days.  The  test  showed 
that  boiler  No.  I,  which  received  the  waste  gases,  developed  406.8 
B.  H.  P.,  of  which  it  was  calculated  that  264  B.  H.  P.  was  pro- 
duced by  the  waste  heat  from  the  two  kilns  and  the  remainder 
from  coal  burned  on  the  grate.  When  boiler  No.  2  was  tested, 
boiler  No.  I  received  the  heat  from  the  waste  gases  of  two  kilns 
and  no  heat  from  hand  firing,  and  during  this  time  a  measurement 
of  the  feed  water  indicated  that  the  heat  from  the  waste  gases  was 
sufficient  to  produce  254  B.  H.  P.,  which  roughly  checks  the  pre- 
ceding test. 

Practically  all  cement  manufacturers  realize  the  great  loss  of 
heat  due  to  the  high  temperature  of  the  kiln  gases,  and  it  is  only  a 
question  of  time  until  all  plants  will  have  adopted  some  method 
of  saving  this  waste  heat.  The  long  kiln  seems  to  be  the  favorite 
method  at  present  adopted  by  the  newer  mills,  and  many  of  the 
old  ones  are  lengthening  their  kilns  to  from  100  to  120  feet.  While 
the  long  kiln  will  effect  some  economy  the  80  and  loo-foot  kilns 
will  still  be  quite  wasteful,  for  if  the  6o-foot  kiln  only  absorbs  20 
or  30  per  cent,  of  the  heat  of  combustion,  it  would  seem  as  if 

1  Sibley  Journal  of  Engineering,  March,  1904;  also  Concrete,  November,  1904. 


KILNS  AND  BURNING  145 

Prof.  Carpenter's  plan  of  utilizing  the  kiln  gases  in  a  boiler  would 
really  effect  the  greater  economy.  The  difficulty  that  has  kept  the 
cement  manufacturer  from  making  use  of  the  hot  blast  stoves  of 
the  iron  manufacturer,  namely,  the  large  quantity  of  dust  in  the 
kiln  gases,  has  also  interfered  somewhat  with  the  previous  at- 
tempts to  use  the  waste  gases  under  boilers,  but  I  believe  Prof. 
Carpenter  claims  to  have  eliminated  this  trouble. 

From  some  observations  made  on  the  flue  gases  of  the  i5O-foot 
kilns  I  am  confident  that  in  order  to  reduce  the  kiln  gases  to 
400°  F  the  temperature  obtained  in  good  boiler  practice,  it  would 
be  necessary  to  lengthen  these  kilns  to  at  least  250  feet.  In  this 
connection  it  may  be  said  that  the  diameter  of  the  kiln  will  have 
some  effect  on  the  economy.  The  smaller  the  diameter  for  a 
given  length  the  greater  the  economy.  To  decrease  the  diameter 
however,  is  to  decrease  the  capacity  because  it  decreases  the  coal 
which  can  be  burned. 


CHAPTER  VIIL 


COOLING  AND  GRINDING  THE  CLINKER,  STORING 
AND  PACKING  THE  CEMEMT,  ETC 


Cooling  the  Clinker. 

The  clinker  leaves  the  kiln  at  a  temperature  of  about  2100°  F. 
It  is,  of  course,  entirely  too  hot  to  grind  and  must  be  cooled.  It 
has  generally  been  found  preferable  to  do  this  mechanically  in- 
stead of  letting  the  clinker  lie  in  heaps  and  cool  of  itself.  In 
some  mills  this  has  been  done  in  pits,  in  others  in  rotary  coolers, 
but  the  majority  of  the  mills  use  the  upright  cooler  shown  in  Fig. 
33.  This  consists  of  an  upright  steel  cylinder  about  8  feet  in 
diameter  and  35  feet  high  provided  as  shown  with  baffle  plates 
and  shelves.  As  the  clinker  falls  over  these  it  meets  a  current  of 
air  blown  in  through  a  perforated  pipe  running  up  through  the 
centre  of  the  cylinder  and  is  thus  cooled.  There  is  usually  one 
cooler  to  each  pair  of  kilns.  The  clinker  is  lead  from  these  lat- 
ter by  chutes  to  a  common  bucket  elevator  which  carries  it  to  the 
top  of  the  cooler.  Usually  water  is  added  to  the  clinker  in  a 
steady  stream  as  it  falls  into  the  elevator  pit.  This  helps  to  cool 
the  clinker,  makes  it  more  brittle  and  easier  to  grind  in  the  ball 
mill  and  saves  the  elevator  from  handling  such  very  hot  material. 
There  is  probably  nothing  in  the  curing  of  the  cement  or  the  hy- 
dration  of  the  free  lime,  since  any  of  the  former  present  is  usually 
locked  up  in  the  interior  of  the  clinker.  It  may,  however,  pre- 
vent the  crystallization  of  the  more  soluble  di-calcium  aluminate 
from  the  magma  of  the  clinker  and  so  help  the  quality  of  the  ce- 
ment. The  writer  has  frequently  cooled  clinker  suddenly  by 
plunging  it,  red  hot  from  the  mouth  of  the  kilns,  into  water.  The 
only  perceptible  effect  is  to  bleach  the  color  from  dark  greenish 
black  to  nearly  white.  If  this  clinker  is  dried  and  ground,  it  will 
be  found  to  have  pretty  much  the  same  properties  as  clinker 
caught  at  the  same  time  and  allowed  to  cool  slowly  in  air. 
The  writer  has  never  observed  that  unsound  cement  could  be 


COOLING,  GRINDING  AND  STORING  OF  CEMENT 


made  sound  by  this  process.  It  does  take  up  some  water 
(probably  on  the  outside  of  the  lumps  only,  however),  as  a  loss 
on  ignition  test  will  show.  Such  clinker  is  easily  ground  and  the 
resulting  cement  trowels  nicely.  This  greenish  white  color  of 


Fig-  33-    Upright  Clinker  Cooler  (Mosser  &  Son.) 

water  cooled  clinker  is  probably  the  normal  color  of  the  cement 
clinker  when  hot,  as  in  this  state  all  compounds  are  in  solution 
in  the  fusible  magma  of  the  clinker.  On  cooling  slowly  the  iron 


I4  PORTLAND  CEMENT 

separates  out  as  black  magnetic  oxide  of  iron,  Fe,O4,  but  on  sud- 
denly cooling  it  does  not  have  time  to  do  this. 

The  clinker  is  usually  drawn  from  the  bottom  of  the  cooler  on 
to  belt  conveyors,  or  else  into  barrows  and  carried  to  an  elevator, 
which  carries  it  up  to  the  bins  above  the  ball  mills  or  rolls,  which 
ever  are  used  to  grind  the  clinker. 

Some  mills  use  a  rotary  cooler  which  consists  of  a  steel  shell 
similar  to  that  of  the  kiln  and  mounted  on  friction  rollers  just 
as  the  kiln  is.  Usually  this  is  lined  with  fire  brick.  One  cooler 
is  used  for  two  kilns  and  air  is  blown  up  through  the  cylinder  to 
cool  the  clinker.  Such  coolers  act  as  pre-heaters  to  the  air  en- 
tering the  kiln.  A  form  of  cooler  used  by  one  of  the  New  York 
State  mills  recently  came  to  the  writer's  notice.  It  consisted  of  a 
water  jacketed  revolving  cooler.  The  water  entering  and  leav- 
ing the  jacket  through  pipes  leading  from  a  specially  designed 
feeder  placed  in  the  centre  of  the  discharge  end  of  the  cooler. 
The  water  after  leaving  the  cooler  was  used  in  the  boilers,  the 
cooler  simply  acting  as  a  preheater.  These  coolers  are  said  to 
have  worked  well,  and  to  have  cooled  the  clinker  perfectly. 

Cooling  clinker  in  pits  has  been  tried  at  a  number  of  places, 
but  does  not  seem  to  have  worked  very  well  anywhere.  Some 
few  mills  convey  their  clinker  red  hot  out  into  the  fields  and 
allow  it  to  cool  naturally.  Such  clinker  is  easily  ground  and  has 
usually  absorbed  some  moisture  so  that  for  every  100  barrels  of 
clinker  burned  the  manufacturer  should  grind  from  101  to  104 
barrels.  A  sort  of  case  of  watered  stock,  except  that  in  this  case 
the  water  probably  does  some  good.  The  great  difficulty  with 
this  system  of  storage  is  the  conveying  of  the  red  hot  clinkers  out 
into  the  fields.  Getting  them  back  to  the  mill  is,  of  course,  easy 
as  any  of  the  coal  handling  devices,  such  as  aerial  cables  and 
orange  peel  buckets,  which  will  do  this  satisfactorily,  or  tunnels 
provided  with  belt  conveyors  under  the  piles  may  be  used. 

Grinding  the  Clinker. 

The  clinker  is  ground  in  Griffin  mills  or  ball  and  tube  mills,  all 
of  which  have  been  described  in  the  section  on  grinding  the  raw 
materials.  At  the  mills  of  the  Atlas  Portland  Cement  Co.  the 
clinker  is  ground  in  Huntington  mills  and  at  one  or  two  mills  the 


COOLING,  GRINDING  AND  STORING  OF  CEMENT 


149 


Kent  mill  is  being  used  for  this  purpose.  It  is  usual  for  the  clink- 
er to  be  ground  by  the  same  type  of  machinery  as  is  used  to  grind 
the  raw  material.  The  principal  reason  for  this  is  that  only  one 
set  of  repair  parts  have  to  be  carried  in  stock.  A  number  of 
mills,  however,  use  ball  and  tube  mills  to  grind  the  raw  materials 
and  Griffin  mills  to  grind  the  clinker,  the  idea  being  that  the  for- 
mer is  the  better  of  the  two  for  soft  materials,  and  the  latter  the 
more  suited  to  the  hard  clinker.  The  tube  mill  is  also  a  splendid 
mixer  for  hard  and  soft  materials,  such  as  clay  and  limestone. 
The  tube  mill  is  also  well  suited  to  wet  grinding,  and  hence  to 
marl  and  clay. 

Kent  Mill. 

This  is  a  new  mill  which  has  so  far  been  used  in  connection 
with  some  form  of  separator,  both  to  prepare  material  for  the 
tube  mill  and  also  to  do  the  final  grinding.  This  mill,  the  prin- 


ADJUSTIN 
SCREW 


Fig.  34.     Kent  Mill. 

ciple  of  which  is  illustrated  in  Fig.  34,  consists  of  a  vertical  re- 
volving ring,  having  three  grinding  rolls  which  are  mounted  on 
horizontal  shafts  and  which  press  against  the  inner  surface  of  the 
ring.  The  material  to  be  ground  is  fed  on  the  inner  surface  of 
the  ring  and  is  ground  between  this  and  the  rolls.  The  inner 
surface  of  the  ring  is  slightly  concave  and  the  cement  is  kept  in 


15°  PORTLAND  CEMENT 

the  center  of  this  and  between  the  ring  and  rolls  by  centrifugal 
force. 

The  Kent  mill  requires  the  use  of  an  outside  separator;  that 
is,  the  material  as  delivered  by  the  mill  itself  consists  of  both 
coarse  and  fine  particles,  and  the  latter  must  be  separated  from 
the  mixture,  and  the  former  returned  to  the  mill  for  further 
grinding.  At  the  plant  of  the  Newago  Portland  Cement  Co., 
where  the  Kent  mill  is  used,  a  shaking  screen  of  wire  cloth  has 
been  devised  for  this  purpose,  but  the  majority  of  the  manufac- 
turers w7ho  are  experimenting  with  the  Kent  mill  are  using  the 
Emerick  separator  or  the  Pfeiffer  separator.  Both  these  machines 
are  similar  in  principle,  and  make  use  of  a  current  of  air  to  sepa- 
rate the  fine  from  the  coarse  particles. 

Air  Separators. 

The  Pfeiffer  separator  is  much  used  in  Germany  and  Europe 
to  take  out  the  fine  material  from  the  product  of  the  ball  mill, 
and  so  relieve  the  tube  mill  of  some  of  its  work.  The  separator 
is  shown  (in  section)  in  Fig.  35.  It  consists  of  an  outer  and 
an  inner  cone  of  sheet  metal  as  shown  in  the  drawing.  The  mate- 
rial to  be  separated  is  fed  into  the  mill  through  the  hopper  on  to 
a  plate,  which  is  connected  to  a  vertical  shaft,  and  is  revolved  at 
a  speed  of  about  200  revolutions  per  minute.  The  material  is 
thrown  off  this  plate  in  a  thin  spray,  by  centrifugal  force,  and  is 
met  by  a  current  of  air,  going  in  the  direction  shown  by  the 
arrows.  The  coarse  particles  fall  through  this  current  into  the 
inner  case,  and  the  finer  ones  are  carried  into  the  outer  space, 
between  the  inner  and  outer  cones.  The  air  currents  are  main- 
tained by  the  fans  as  shown. 

At  the  plant  of  the  Hudson  Cement  Co.  the  separators  are  used 
after  the  tube  mills.  The  grit  passes  directly  from  the  ball  mills 
through  the  tube  mills  and  from  the  latter  to  the  separators.  The 
fine  material  is  sent  from  the  separators  to  the  stock  house,  and 
coarse  particles  are  returned  to  the  tube  mill.  The  separators  in- 
creased the  capacity  of  the  tube  mills  from  8  barrels  per  hour, 
of  a  fineness  of  from  93  to  94  per  cent,  through  a  No.  100  sieve, 
to  13  to  15  barrels  per  hour,  of  a  fineness  of  96-98  per  cent, 
through  a  No.  100  sieve. 


COOLING,  GRINDING  AND  STORING  OF  CEMENT 


At  one  of  the  mills  of  the  Lehigh  District,  a  Kent  mill  working 

ill 


Fig.  35.     Pfeiffer  Air  Separator. 

in  combination  with  a  Pfeiffer  separator  ground  n  barrels  of 


152  PORTLAND  C£M£NT 

cement  per  hour  with  an  expenditure  of  about  30  horse-power 
for  the  mill,  separator  and  attendant  elevators  and  conveyors. 
The  mill  itself  requires  about  25  horse-power  and  the  separator 
from  i  to  2  horse-power. 

As  has  been  said  the  use  of  separators  to  take  out  the  fine  par- 
ticles from  the  ball  mill  product  and  so  relieve  the  tube  mill  of 
part  of  its  work  is  quite  general  in  Germany,  but  so  far  has  not 
been  tried  to  any  extent  in  this  country.  A  ball  mill  provided 
with  i6-mesh  screens  of  No.  23  wire  will  give  a  product  con- 
taining between  15  and  20  per  cent,  of  material  passing  a  No. 
200  test  screen.  The  Kominuter  on  the  other  hand  gives  a  much 
larger  percentage  of  fine  material,  as  would  be  supposed  since 
the  material  must  travel  from  end  to  end  of  the  drum  before  pass- 
ing out,  while  in  the  ball  mill  it  falls  through  the  plates  and 
screens  as  soon  as  ground.  A  test  of  the  Kominuter  product 
made  by  the  writer  gave  25  per  cent,  passing  through  a  No.  200 
sieve  and  40  per  cent,  through  a  No.  100  sieve.  In  this  case  the 
screens  were  16  mesh  and  of  No.  23  wire.  A  finer  mesh  screen 
on  either  ball  mill  or  Kominuter  will,  of  course,  give  a  product 
containing  more  fine  material.  This  fine  material  from  the  Komi- 
nuter contains  considerable  flour  as  sand  briquettes  made  of  the 
material  passing  a  No.  200  sieve  gave  335  Ibs.  for  7  days  and  447 
Ibs.  for  28  days.  The  material  passing  the  No.  100  sieve  gave  267 
Ibs.  for  7  days  and  320  Ibs.  for  28  days. 

The  Emerick  separator  is  similar  in  principle  to  the  Pfeiffer, 
but  differs  from  it  somewhat  in  construction.  It  has  been  tried 
with  marked  success  by  one  plant  in  the  Lehigh  Valley.  In  this 
mill  the  addition  of  a  9-foot  Emerick  separator  after  the  mill  in- 
creased the  output  of  one  of  their  tube  mills  from  9  barrels  of 
cement  per  hour  to  18  barrels  per  hour — grinding  in  both  cases 
to  the  same  fineness,  75%  through  a  No.  200  sieve.  Part  of  this 
increased  output  was,  however,  due  to  more  efficient  working  of 
the  tube  mill  itself.  In  the  same  mill  a  10  foot  separator  increased 
the  output  of  a  tube  mill  from  1 1  barrels  per  hour  to  24  barrels  per 
hour.  The  entire  grinding  plant  of  the  Buckhorn  Portland  Ce- 
ment Co.  is  equipped  with  these  separators,  and  they  are  being 
given  a  trial  by  American  cement  manufacturers  generally,  about 


COOLING,  GRINDING  AND  STORING  OF  CEMENT  153 

50  of  them  having  been  placed  in  the  different  mills  during  the 
past  six  months. 

A  rather  amusing  discussion1  of  the  separator  question  appear- 
ed in  one  of  the  engineering  magazines,  about  a  year  ago,  in 
which  the  author  took  the  ground  that  the  separators  destroy  the 
uniformity  of  the  product  and  that  for  example  in  a  clay-lime- 
stone mixture  the  lighter  particles  of  clay  would  be  blown  away 
from  the  heavier  limestone.  The  author  seems  to  have  overlooked 
the  fact  that  by  pulverizing  the  limestone  particles  a  little  finer 
they  too  will  be  blown  out  by  fans  of  the  separator  so  that  while 
it  may  be  true  that  on  starting  up  a  new  separator  the  first 
product  will  be  slightly  over-clayed,  the  trouble  will  be 
adjusted  by  the  return  of  the  limestone  to  the  grinder 
for  finer  pulverizing,  after  which  it  will  be  blown  out  on 
its  next  passage  through  the  separator  together  with  the  clay 
from  the  new  lot  of  mix  fed  into  the  tube  mill,  the  process  being 
a  continuous  one.  This  same  objection  can  be  raised  against  ball 
mills  that  the  softer  particles  of  clay  or  cement  rock  will  be  pul- 
verized sooner  and  drop  through  the  screens  of  the  ball  mill  be- 
fore the  limestone.  In  this  case  also  this  irregularity  adjusts  it- 
self and  in  the  same  manner.  My  own  personal  experience  with 
air  separation  at  the  plant  of  the  Edison  Portland  Cement  Co. 
convinces  me  that  there  is  nothing  against  its  use  on  the  ground 
of  lack  of  uniformity  in  the  product.  In  the  Griffin  mill  the  sepa- 
ration of  the  finer  from  the  coarser  particles  is  effected  by  air 
separation,  as  the  fans  placed  on  the  shaft  blow  the  fine  material 
through  the  screen. 

Stock  Houses. 

From  the  grinding  mills  the  finished  cement  goes  to  the  stock 
house.  This  usually  consists  of  a  long  low  frame  building  divid- 
ed into  bins,  by  means  of  wooden  partitions,  so  that  each  day's 
grinding  may  be  kept  separate.  These  bins  usually  hold  from 
1 000-2000  barrels  and  are  arranged  either  on  each  side  of  a  cen- 
tral aisle  or  else  with  an  aisle  on  each  side.  The  parts  of  the 
bins  facing  the  aisles  are  stopped  up  by  means  of  boards  which 
may  be  easily  removed,  and  below  the  floor  of  the  aisles,  run 

1  "  Some  of  the  Reasons  Why  Separators  are  not  Used  in  Portland  Cement  Works." 
E.  C.  Eckel,  Engineering  News,  Vol.  1,1.,  p.  344. 


154  PORTLAND   CEMENT 

screw  conveyors  to  the  packing  room,  which  is  usually  one  end  or 
a  large  room  in  the  middle  of  the  stock  house.  The  screw  con- 
veyors are  covered  with  boards,  except  in  front  of  the  bins  where 
gratings  three  of  four  feet  in  length  are  placed.  The  cement  is 
usually  brought  in  from  the  grinding  mills  by  an  overhead  screw 
conveyor,  from  the  trough  of  which  spouts  run  to  the  middle 
of  the  bins.  The  openings  in  the  trough  leading  into  the  spouts 
are  closed  by  iron  slides  or  gates  so  that  the  cement  may  be  run 
into  any  bin  desired  at  any  time.  When  it  is  desired  to  open  a 
bin  the  bottom  plank  is  removed  from  the  front  of  the  bin  and 
the  cement  is  allowed  to  run  into  the  screw  conveyor,  through  the 
grating.  When  it  ceases  to  run  of  itself,  a  scraper,  which  con- 
sists of  a  flat  iron  plate  about  6"  X  18"  from  the  middle  of  which 
a  long  handle  projects,  is  introduced  and  all  of  the  cement  which 
can  be  pulled  through  the  opening  conveniently  is  drawn  into 
the  conveyor,  after  which  the  remainder  of  the  boards 
are  taken  down,  and  the  rest  of  the  cement  is  drawn 
into  the  conveyor,  either  with  the  scraper  or  wheeled  by 
barrows  to  the  grating.  To  do  away  with  the  manual  labor 
required  by  such  a  method  of  opening  a  bin,  stock  houses 
provided  with  tunnels  running  under  the  bins  are  used.  The  con- 
veyors are  located  in  the  tunnel  and  the  bins  are  fixed  with  slop- 
ing floors  and  spouts,  which  deliver  into  the  conveyor.  A  simpler 
method  and  one  which  is  adapted  to  the  improvement  of  old 
stock  houses  is  to  put  in  small  conveyors  running  across  the  bins 
and  emptying  into  the  main  conveyors.  The  stock-house  of  the 
Illinois  Steel  Co.,1  consists  of  four  cylindrical  Monier  concrete 
steel  bins  in  a  group.  The  bins  are  25  feet  in  diameter  and  53 
feet  high  and  hold  about  7,500  barrels  each.  The  cement  is  tapped 
out  below. 

Packing. 

Cement  is  packed  into  wooden  barrels  holding  380  Ibs.  or  into 
paper  or  cloth  bags  holding  95  Ibs.  by  means  of  packers,  such  as 
are  used  for  packing  flour.  The  cement  is  packed  as  shipped  and 
the  bags  or  barrels  are  trucked  directly  to  the  cars.  For  this 
reason  the  packing  room  should  be  so  arranged  that  the  cars  to  be 
loaded  can  be  brought  alongside  of  the  room  and  a  shed  roof 

1  Cement,  III,  4,  286  ;  Cement  and  Engineering  News,  1903,  p.  55. 


COOLING,  GRINDING  AND  STORING  OF  CEMENT  155 

should  be  run  out  over  the  cars  so  the  loading  will  not  be  in- 
terrupted by  rainy  weather.  Since  some  seasons  of  the  year  are 
much  busier  than  others,  the  packing  house  should  be  able  to  load 
and  ship  at  least  twice  as  much  cement  as  the  mill  can  make  in  a 
day.  The  floor  of  the  packing  room  should  be  on  a  level  with 
the  floor  of  the  cars  to  be  loaded.  Cloth  bags  are  used  much 
more  for  packing  cement  than  anything  else.  In  the  case  of 
cloth  bags  the  consumer  is  charged  with  the  value  of  the  bag,  10 
cents,  and  credited  by  7^2  cents  when  the  bag  is  returned.  The 
bags  are  all  marked  with  the  label  of  the  brand  and  so  each 
manufacturer  knows  his  own  bags.  Barrels  and  paper  bags  are 
sold  to  the  customer  and  are  not  returnable. 

Nearly  all  cement  mills  have  a  cooper  shop  connected  with  the 
mill.  Some  of  these  shops  are  equipped  with  barrel  making  ma- 
chinery, and  at  others  all  the  work  is  done  by  hand. 

Power  Plant. 

The  grinding  proposition  of  a  modern  cement  mill  is  one  of 
considerable  magnitude.  A  1000  barrel  a  day  plant  must  grind 
about  500  tons  of  material  to  an  almost  impalpable  powder  every 
twenty-four  hours.  Three  hundred  tons  of  this  represent  the 
raw  material  which  must  be  reduced  from  pieces  of  stone  as 
large  as  a  man  can  handle  to  such  a  degree  of  fineness  that  from 
90  to  98  per  cent,  of  the  powder  will  pass  a  loo-mesh  test  sieve. 
The  other  200  tons  represents  the  slag  like  clinker  which  must 
be  pulverized  so  fine  that  at  least  92  per  cent,  of  it  will  pass  this 
sieve.  The  power  required  to  run  the  amount  of  machinery  nec- 
essary to  grind  this  quantity  of  material  is  probably  greater  than 
that  which  would  be  utilized  in  the  manufacture  of  a  similar  value 
of  any  other  commodity. 

The  size  of  the  power  plant  which  will  be  required  in  manufac- 
turing looo  barrels  of  cement  per  day  will  depend  largely  upon 
the  class  of  material  to  be  ground,  upon  the  type  of  machinery 
used  to  do  this,  the  thoroughness  with  which  it  is  done,  as  well 
as  the  proper  installation  of  the  plant  itself  and  the  means  of 
transmitting  the  power  to  the  machinery.  The  cheapness  with 
which  cement  can  be  manufactured  will  hinge  largely  on  these 
points  and  hence  the  power  plant  of  an  up-to-date  cement  mill 


156  PORTLAND  C£M£NT 

must  be  "dead  right"  and  embody  the  most  economic  devices  for 
the  production  and  use  of  steam.  The  boilers  must  be  of  the  most 
improved  type  and  the  engines  of  the  most  modern  pattern.  The 
latter  must  be  heavily  made  and  able  to  stand  continual  heavy 
duty.  The  general  character  of  the  power  generators  themselves 
and  the  arrangement  of  the  engine  and  boiler  rooms  is  similar 
to  that  of  other  manufacturing  enterprises  where  much  slow  mov- 
ing heavy  machinery  is  employed.  Not  only  must  the  engines 
and  boilers  be  of  the  proper  type,  but  the  distribution  of  the  pow- 
er to  the  mills  must  be  effected  with  the  least  possible  loss  due 
to  friction.  To  this  end  short  powerful  shafts  are  used  which  are 
driven  by  belting  or  rope  drivers,  directly  from  the  engines,  and 
which  transmit  the  power  to  crushers,  and  grinding  mills.  In 
some  mills  the  engines  are  connected  direct  or  by  belting  to  pow- 
erful electric  generators  and  the  current  from  these  is  carried 
about  the  mills  by  copper  cables  and  distributed  to  motors  which 
are  directly  connected  by  gearing  to  the  mills.  Where  water 
power  is  at  hand  the  generators  have  been  connected  to  power- 
ful turbines  and  power  thus  very  cheaply  obtained.  It  is  also 
proposed  to  utilize  the  power  in  the  waste  gases  from  blast  fur- 
naces for  cement  manufacture.  At  the  new  plant  of  the  Illinois 
Steel  Co.,  at  Buffington,  Ind.,  the  waste  energy  in  the  gases  from 
the  iron  furnaces  of  this  company  at  Joliet,  Illinois,  is  to  be 
converted  into  electrical  power  and  transmitted  some  eight  miles 
over  the  Chicago  River  to  the  cement  plant. 

In  designing  the  power  plant  of  a  cement  mill,  it  has  usually 
been  found  best  to  run  the  mills  grinding  raw  material  with  one 
engine  and  those  grinding  clinker  by  another,  rather  than  to  use 
one  large  engine  for  both.  It  has  also  been  found  best  to  run 
the  kilns  by  a  separate  engine  so  that  shut  downs  may  be 
avoided. 

The  actual  power  which  will  be  required  by  any  cement  mill, 
as  we  have  said  before,  will  depend  entirely  upon  circumstances. 
To  operate  a  mill  making  1000  barrels  of  cement  from  cement 
rock  and  limestone  will  require  at  least  1000  horse-power.  A  mill 
of  this  size,  working  on  marl  and  clay,  will  require  a  little  less, 
while  one  on  clay  and  limestone  will  require  a  little  more.  In 


XIX.-SHOWI> 


Mill. 

Quarry  Equipment. 

For  Preparatory  Treat- 
ment. 

- 

i.  Dry  Process. 
Cement  rock  only. 
Capacity,  800  bbl.  daily. 

Side  dump  cars,  (2^  T). 
Incline  railway, 
i  Steam  hoist, 
i  Electric  hoist. 
3  Air  drills. 

i  Gates  crusher,  (No.  6). 
i  Storage  bin,  (3.500  T;. 
i  Rotary  dryer,  (4'  x  35'). 

2.  Dry  Process, 
limestone  and  shale. 
Capacity,  1,500  bbl.  daily. 

Crusher  plant  located    at 
quarry, 
i  Gates  crusher.  (No.  5). 
i  Gates  crusher,  (No.  8). 
2  Rotary  screens. 
Steel  cars,  (50  T;. 

Rock  crusher  in  the  quarry. 
Coarse  rock  sold  for  ma- 
cadam, fines    only    used 
for  cement. 
4  Rotary  dryers,  (54"  x  50'). 

3.  Dry  Process. 
Cement  rock    and   lime- 
stone. 
Capacity,  3,000  bbl.  daily. 

Side  dump  cars,  (3  T). 
Endless  cable. 
Automatic  car  dump. 

2  Gates  crushers,  (No.  6). 
2  Motors,  (60  H.  P.). 
3  Dryers,   (4o"-65"  x  40'. 
i  Motor,  (15  H.  P.). 
i  Storage  bin. 

- 

4.  Dry  Process. 
Cement    rock  and    lime- 
stone. 
Capacity,  2,500  bbl.  daily. 

Side  dump  cars. 
Gravity  to  mill. 
Hoist  and  gravity  back  to 
quarry. 
Air  drills. 

2  Austin  crushers,  (No.  6) 
2  Sets  rolls. 
2  Dryers,  (6'  x6o'). 
i  Storage  bin 

5.  Dry  Process. 
Limestone  and  clay. 
Capacity.  1,000  bbl.  daily. 

2  Gates  crushers   (No.  5). 
i  Td.  Cm.  engine,  (150  H.P.) 
2  Tubular  boilers,  (100  H. 
P.  e.) 
Barges,  (500  T). 
Rock  crushed  in  quarry  and 
sent  to  mill  by  water  in 
barges, 

i  Unloading    derrick    and 
cars  to  the  mill. 
3  Dryers,  (6'  x  60'). 
Storage  bins. 

6.  Wet  Process. 
Marl  and  clay. 
Capacity,  500  bbl.  daily. 

i  Dipper  dredge, 
i  Barge. 
6"  Pipe  line  to  mill. 

i  Marl  tank, 
i  Dry  pan  for  clay, 
i  Pug  mill, 
i  Slurry  tank. 

7.  Wet  Process. 
Marl  and  clay. 
Capacity,  1,000  bbl.  daily. 

i  Dipper  dredge. 
i  Stone  separator. 
2  Scows,  (50  cu.  yds), 
i  Steam  tug. 
2  Marl  pumps,  8"  pipe  line. 

2  Marl  tanks,  (14'  diam.). 
i  Clay  bin. 
i  Dry  pan. 
i  Pug  mill. 

8.  Wet  Process. 
Marl  and  clay. 
Capacity,  500  bbl.  daily. 

i  Dipper  dredge. 
Cars. 
Track  and  incline  railway 
to  mill. 

i  Rotary  clay  dryer, 
i  Williams'  mill. 
3  Storage  clay  bins, 
i  Pug  mill. 
3  Slurry  vats,  (10'  x  10'). 

Abbreviations  :    bbl—  Barrels  ;  T—  Tons  ;  H.  P.  e.—  Horse-power  each  ;  K.  W.  e. 
1  From  published  descriptions. 

-SHOWING  THE  MECHANICAL  EQUIPMENT  OF  SOME  MODERN  PORTLA 


ory  Treat- 

t. 

For  Grinding  the  Raw 
Materials. 

Kilns,  etc.,  for  Burning. 

For  Cooling  and  Grinding 
the  Clinker. 

r,  (No.  6). 
(3.500  T;. 
,  U'x35'). 

3  Ball  mills,  (No.  7). 
2  Tube  mill,  (5'6"x22'). 

4  Rotary  kilns,  (6'  x  60'). 
4  Motors,  (71A  H.  P.  e.). 
3  Fans  with  motors. 

2  Upright  coolers,  (8'  x  32') 
2  Ball  mills,  (No.  7). 
i  Kominuter. 
2  Tube  mills,  (5*6"  x  22  ). 
i  Tube  mill,  (5'  x  22') 

i  the  quarry. 
>  (1  for  ma- 
only    used 

s,  (54"  x  50'). 

5  Kominuters. 
6  Tube  mills,  (s'6"x22'). 

8  Rotary  kilns,  (6'  x  60'). 
8  Motors,   (15  H.  P.  e.). 
i  Blower. 
2  Motors,  (50  H.  P.  e.) 

8  Galschiot  coolers. 
2  Coffee-mill  crushers. 
6  Kominuters. 
6  Tube  mills,  (s'6"  x  22'). 
i  Traveling    crane    and 
buckets. 

•s,  (No.  6). 
.  P.). 
,5"  x  40'. 

K). 

7  Ball  mills,  (No.  8). 
7  Motors,  (60  H.  P.  e.). 
7  Tube  mills,  (5'  x  22'). 
7  Motors,  (100  H.  P.  e.). 
i  Motor,  (40  H.  P.)  for  ele- 
vators, etc. 

16  Rotary    kilns,    (7'-5'6'  x 
60').     ' 
2  Motors,  (180  H.  P.  e.). 

8  Rotary  coolers  (23'xs'). 
8  Upright  coolers,  (8'  x  32'). 
9  Ball  mills,  (No.  8). 
9  Motors,  (60  H.  P.  e.). 
ii  Tube  mills,  (5'  x  22'). 
ii  Motors,  (100  H.  P.  e.). 

•rs,  (No.  6) 
So'). 

8  Three  Roll  Griffin  mills. 

6  Rotary    kilns,  (7'-s'6"  x 
100'). 

3  Upright  coolers. 
3  Coffee-mill  crushers. 
3  Sets  rolls. 
24  Griffin  mills. 

errick    and 
'.11. 

00'). 

3  Ball  mills,  (No.  7). 
3  Tube  mills,  (5'  x  22'). 

4  Rotary  kilns,  (f  x8o'). 
Motors. 
Blowers,  etc. 
(Boilers    are    heated    by 
waste  heat  of  kilns.) 

i  Set  rolls. 
Clinker  storage,  (52'  x  120') 
10  Griffin  mills. 

lay. 

i  Tube  mill,  (5'  x  22'). 
i  Ground  slurry  vat. 
4  Ground  slurry  tanks,  (14' 
diam.  x  16'  high). 

4  Rotary  kilns,  (6'  x  60'). 

Floor  for  cooling  clinker. 
5  Griffin  mills. 

14'  diam.). 

3  Emery  mills,  (42"), 
2  Slurry  pits,  (12'  x  84'). 
2  Tube  mills,  (5'  x  22'). 
i  Slurry  vat,  (29^x87^')- 

9  Rotary  kilns,  (6'  x  60'). 
i  Engine,  (8'  x  10'). 
i  Blast  fan,  (120"). 

i  Rotary  cooler. 
4  Ball  mills,  (No.  7). 
2  Tube  mills,  (5'  x  22'). 

Iryer. 

11 
bins. 

to'xio'). 

2  Tube  mills  (s'6"  x  22'). 
10  Ground  slurry  pits,  (10 
x  10'). 

4  Rotary  Kilns,  (6'  x  60'). 
Blast  fans,  etc. 

2  I^athbury   &  Spackman 
Regenerative  coolers. 
3  Ball  mills,  (No.  7). 
2  Tube  mills,  (s'6"  x  22'). 

ich  ;  K.  W.  e.— Kilowatts  each  ;  Cm.  Cd.—Cpm  pound  Condensing  ;  Td.  Cm.— Tandem  Compound  ;  D.  C 


,AND  CEMENT  PLANTS.1 


lg 

Main  Power  Plant. 

Auxiliary  Power  Plant. 

Kiln  Fuel  Plant. 

O- 

2  Cm.  Cd.  engines,  (500  H. 
P.  e.). 
i  Boiler,  (300  H.  P.  e.) 
4  Boilers,  (150  H.  P.  e.). 
Pumps,  condensers,  etc. 

i  Engine,  (75  H.  P.). 
i  Air  compressor, 
i  D.C.  generator,  (175  K.W.) 
2  D.C.generarors,  (50  K.  W.e} 
i  Fire  pump,  (750  gals). 

i  Mosser  dryer, 
i  Set  rolls, 
i  Tube  mill  (s'6"  x  22'). 

2  Cm.  Cd.  engines,  22"  x  44" 
x  48". 
6  Boilers. 
Pumps,  condensers,  etc. 

2  Td.  Cm.  engines,  (400  H. 
P.  e.). 
2  D.  C.  generators,  (200  K. 
W.  e.). 

i  Cuminer  dryer, 
i  Bartlett  &  Snow  dryer, 
i  Set  disintegrating  rolls. 
2  Emery  mills. 
2  Tube  mills,  (s'6"  x  22'). 

•>>. 

3  Generators,  (800  K.W.  e.) 
and  3  engines,  direct  con- 
nected. 
7  Boilers,  (400  H.  P.  e.)  and 
Mechanical  stokers. 
Pumps,  condensers,  etc. 

i  Generator.  (50  K.W.)  and 
i  Engine,  direct  connected, 
i  Air  compressor,  (165  H.P.) 
i  Small  air  compressor, 
i  Fire  pump. 

i  Crushing  roll. 
3  Dryers,  (4'  x  35'). 
i  Stedman  disintegrator. 
3  Tube  mills,  (s'6"  x  22'). 

2  Cm.   Cd.   engines,  (1,500 
H.  P.  e.). 
8  Upright  boilers,   (300  H. 
P.  e.). 
Pumps,  condensers,  etc. 

i  Generator.  (200  K.W.)  and 
i  Engine,  direct  connected, 
i  Air  compressor. 
2  Generators,  (175  K.W.  e.) 

i  Dryer. 
2  Three  roll  Griffin  mills. 

3')- 

i  Td.  Cd.  engine,  (550  H.  P.) 
i  Td.  Cd.  engine,  (440  H.  P.) 
4  Vertical  water  tube  boil- 
ers, (250  H.  P.  e.)  located 
so  as  to  utilize  waste  heat 
of  kilns. 

2  Del,avall  Steam  turbines, 
(300  H.  P.  e.)  and  genera- 
tors connected. 

i  Set  rolls, 
i  Dryer,  (s'xso'). 
2  Tube  mills,  (s'x22'). 
Motors. 

— 

2  Corliss  engines,    (200  H. 
P.  e.). 
Boilers. 
Pumps,  condensers,  etc. 

Engine  and  direct  connect- 
ed dynamo,  (120  K.  W.) 

Designed  for  use  with  oil. 

2  Corliss  engines,   (750  H. 
P.  e.). 
2  Boilers,  (500  H.  P.  e.). 
2  Boilers,  (250  H.  P.  e.). 
Pumps,  condensers,  etc. 

i  Cm.  Engine  (9"  x  15"  x  9") 
i  D.  C.  Generator(5o  K.W.) 

i  Sturtevant  crusher, 
i  Bartlett  &  Snow  dryer, 
i  Williams  mill,  (No.  3). 
2  Tube  mills,  (s'x22'). 

in 

2  Cm.  Cd.  engines,  (Total 
800  H.  P.) 
3  Boilers  (200  H.  P.  e.). 
Pumps,  condensers,  etc. 

i  Dryer. 
i  Tube  mill,  (s'6"x22'). 

>.  C.— Direct  Current. 


COOLING,  GRINDING  AND  STORING  OF  CEMENT  157 

general,  it  may  be  said  that  it  will  require  from  0.8  to  1.2  horse- 
power for  each  barrel  per  day  capacity  of  the  mill  to  operate  the 
machinery.  Faulty  installation  and  very  hard  raw  materials  may 
easily  run  this  figure  up  to  1.5  horse-power  per  barrel  of  cement 
per  day  capacity.  Roughly  speaking,  about  two-thirds  of  this 
power  will  be  required  to  run  the  grinding  mills ;  and  on  dry 
materials  of  average  hardness,  such  as  limestone  and  cement  rock, 
this  will  be  about  evenly  distributed  between  the  two  grinding  de- 
partments. 

Complete  Equipment  of  Plants. 

Fig.  36  shows  the  arrangement  of  the  machinery  and  the  dis- 
tribution of  power,  etc.,  in  a  modern  wet  process  plant ;  while  Fig. 
37  shows  that  of  a  dry  process  mill.  In  the  latter  all  the  machin- 
ery is  driven  by  motors  directly  connected  to  the  mills  by  gearing. 

Table  XIX  which  follows  shows  the  mechanical  equipment  of 
eight  modern  Portland  cement  plants. 

References  to  Descriptions  of  Plants. 

More  or  less  detailed  descriptions  of  the  following  plants  will  be 
found  in  the  books  and  journals  indicated.  The  plants  marked 
with  an  asterisk  (*)  are  wet  process  plants. 

Alma  Portland  Cement  Co.,  Wellston,  O.  The  Rotary  Kiln1, 
p.  44. 

Alpha  Portland  Cement  Co.,  Alpha,  N.  J.  Engineering  News, 
Vol.  XLIV,  p.  313- 

Alsen's  American  Portland  Cement  Works,  West  Camp,  N.  Y. 
The  Rotary  Kiln,  p.  52 ;  Engineering  Record,  Vol.  XLVII,  p.  10. 

American  Cement  Co.,  Egypt,  Pa.    The  Rotary  Kiln,  p.  66. 

Atlas  Portland  Cement  Co.  Proc.  Inst.  of  Civil  Eng.  (Brit- 
ish), Vol.  CXLV,  p.  57. 

*  Beaver  Portland  Cement  Co.,  Marlbank,  Canada.  The  Rotary 
Kiln,  p.  74;  Cement  and  Engineering  News,  VIII,  p.  72. 

*Bronson  Portland  Cement  Co.,  Bronson,  Mich.  The  Cement 
Industry2,  p.  33.  Engineering  Record,  April  30,  1898. 

1  The  Rotary  Kiln.     206  Pages.     Price,  $2.00.    I^athbury  &  Spackman,  Philadelp  hia 
1902. 

2  The  Cement  Industry.    235  pages.     Price,  $3.00.     McGraw  Pub.  Co.,  New  York. 


158 


PORTLAND  CEMENT 


Fig.  36.    Plan  and  Section  of  the  Egyptian  Portland  Cement  Co.'s  Works  at 
Fenion,  Mich.     (Engineering  Record.) 


COOLING,  GRINDING  AND  STORING  OF  CEMENT  159 

*Buckeye  Portland  Cement  Co.,  near  Bellefontaine,  O.     The 
Cement  Industry,  p.  52;  Engineering  Record,  October  15,  1898. 


Buckhorn  Portland  Cement  Co.,  Manheim,  W.  Va.  Engineer- 
ing News,  Vol.  L,  p.  408. 

*Castalia  Portland  Cement  Co.,  Castalia,  O.  The  Rotary  Kiln, 
p.  78. 


l6o  PORTLAND 

Clinton  Cement  Co.,  Pittsburg,  Pa.    The  Rotary  Kiln,  p.  82. 

Colorado  Portland  Cement  Co.,  Portland,  Colo.  Engineering 
Record,  Vol.  XLIX,  p.  223  and  242. 

Coplay  Cement  Co.,  Coplay,  Pa.  The  Cement  Industry,  p.  20 
and  69.  Engineering  Record,  December  18,  1897;  and  February 
27,  1900. 

*Detroit  Portland  Cement  Co.,  Fenton,  Mich.  The  Rotary 
Kiln,  p.  86. 

Dexter  Portland  Cement  Co.,  Nazareth,  Pa.  Engineering 
Record,  Vol.  L,  160. 

Edison  Portland  Cement  Co.,  near  Stewartsville,  N.  J.  Engi- 
neering Record,  Vol.  XLVIII,  p.  796;  Engineering  News,  Vol. 
L,  555;  Cement  and  Engineering  News,  Vol.  XV,  p.  137. 

*Egyptian  Portland  Cement  Co.,  near  Fenton,  Mich.  Engineer- 
ing Record,  Vol.  XLIX,  p.  320. 

^Empire  Portland  Cement  Co.,  Warners,  N.  Y.  Cement  In- 
dustry, p.  45.  Engineering  Record,  July  16,  1898. 

Hudson  Portland  Cement  Co.,  Hudson,  N.  Y.  Engineering 
News,  Vol.  L,  p.  70. 

*Hecla  Portland  Cement  Co.,  Bay  City,  Mich.  Engineering 
News,  Vol.  LI,  p.  243. 

^International  Portland  Cement  Co.,  Hull,  P.  O.,  Canada.  En- 
gineering Record,  Vol.  LI,  p.  106;  Cement  and  Engineering 
News,  Vol.  XVII,  p.  72. 

lola  Portland  Cement  Co.,  lola,  Kans.  Engineering  and  Min- 
ing Journal,  February  16,  1901. 

Kosmos  Portland  Cement  Co.,  Kosmosdale,  Ky.  Cement  and 
Engineering  News,  Vol.  XVII,  p.  30;  Engineering  Record,  Vol. 
LII,  p.  459- 

Lawrence  Cement  Co.  of  Pennsylvania,  Siegfried,  Pa.  The 
Rotary  Kiln,  p.  96.  The  Cement  Industry,  p.  117.  Engineering 
Record,  May  12,  1900. 

Martin's  Creek  Portland  Cement  Co.,  Martin's  Creek,  Pa.  The 
Cement  Industry,  p.  107.  Engineering  Record,  March  31,  1901. 

2Michigan  Alkali  Co.,  (now  Wyandotte  Portland  Cement  Co.), 
Wyandotte,  Mich.  The  Rotary  Kiln,  p.  1 10 ;  Engineering  News, 
June  7,  1900. 

1  Manufactures  Portland  Cement  from  slag  and  limestone. 

*  Designed  to  use  alkali  waste  and  clay.     Now  uses  limestone  and  clay. 


COOUNG,  GRINDING  AND  STORING  OF  CKMENT  l6l 

^Michigan  Portland  Cement  Co.,  Coldwater,  Mich.  The  Ce- 
ment Industry,  p.  78.  Engineering  Record,  February  25,  1899. 

National  Portland  Cement  Co.,  Martin's  Creek,  Pa.  Engineer- 
ing Record,  Vol.  LI,  p.  288  and  316. 

Nazareth  Portland  Cement  Co.,  Nazareth,  Pa.  The  Cement 
Industry,  p.  85.  Engineering  Record,  December  16,  1899. 

Northampton  Portland  Cement  Co.,  Stockertown,  Pa.  Engi- 
neering Record,  Vol.  XLVIII,  p.  182. 

Pembina  Portland  Cement  Co.,  Milton,  N.  D.  The  Rotary 
Kiln,  p.  124. 

Portland  Cement  Co.,  of  Utah,  Salt  Lake  City,  U.  The  Rotary 
Kiln,  p.  127. 

St.  Louis  Portland  Cement  Co.,  Prospect  Hill,  Mo.  Engineer- 
ing Record,  Vol.  XLVIII,  p.  36. 

Virginia  Portland  Cement  Co.,  Fordwick,  Va.  The  Cement 
Industry,  p.  132;  Engineering  Record,  July  28,  1900. 

Vulcanite  Portland  Cement  Co.,  near  Phillipsburg,  N.  J.  Ce- 
ment Industry,  p.  96.  Engineering  Record,  May  6,  1899. 

*Wabash  Portland  Cement  Co.,  Stroh,  Ind.  The  Rotary  Kiln, 
p.  128. 

^Western  Portland  Cement  Co.,  Yankton,  S.  D.  The  Cement 
Industry,  p.  60.  Engineering  Record,  November  19,  1898. 

Whitehall  Portland  Cement  Co.,  Cementon,  Pa.  The  Cement 
Industry,  p.  142.  Engineering  Record,  September  15,  1900.  Ce- 
ment and  Engineering  News,  Vol.  IX,  p.  23. 

Cost  of  Plant  and  Manufacture. 

A  great  many  itemized  statements,  showing  the  cost  of  erecting 
a  Portland  cement  plant  and  of  manufacturing  a  barrel  of  cement, 
have  been  published  in  the  last  few  years — no  two  of  them  agree- 
ing and  probably  none  of  them  coming  anywhere  near  the  truth. 
For  instance,  in  one  widely  quoted  estimate,  showing  the  average 
cost  of  making  a  barrel  of  Portland  cement  at  an  ideal  2000  barrel 
plant  in  the  Lehigh  District,  the  estimator  has  assumed  that  5  bar- 
rels of  cement  can  be  made  from  one  ton  of  rock ;  whereas,  a  tyro 
chemist  knows  that  the  plant  is  doing  well  which  gets  3.3  barrels 
from  a  ton  of  raw  material.  Very  few  engineers  in  their  esti- 
mates of  the  cost  of  making  a  barrel  of  cement  have  included  de- 

6 


l62  PORTLAND  CEMENT 

preciation  of  buildings  and  the  actual  value  of  raw  material  used. 
This  latter  item  is  an  important  one,  in  spite  of  its  being  over- 
looked. For  example,  suppose  a  mill  using  marl  and  clay  has 
available  a  supply  of  marl  sufficient  for  the  manufacture  of  3,000,- 
ooo  barrels  of  cement,  and  cost  to  erect,  buy  the  land  and  put  in 
operation  $300,000.  Then  10  cents  at  least  should  be  added  to  the 
mill  cost  of  making  a  barrel  of  cement,  because  the  stockholders 
will  have  nothing  for  their  original  expenditure  (except  second- 
hand machinery)  when  they  will  have  made  their  3.000,000  bar- 
rels, and  hence  it  will  have  cost  them  10  cents  a  barrel  more  than 
the  actual  mill  expenditure  to  make  that  quantity  of  cement. 

Similarly,  much  has  been  written  as  to  the  cost  of  building  ce- 
ment plants  and  these  estimates  are  usually  very  much  like  those 
of  cost  and  leave  out  some  important  items.  For  instance,  in  one 
estimate  recently  published  in  a  bulletin  of  one  of  the  state  geolog- 
ical surveys,  the  machinery  is  probably  assumed  to  run  itself,  since 
no  figures  are  given  for  a  power  plant.  Even  experienced  cement 
engineers  often  come  very  wide  of  the  mark  in  their  estimates  of 
the  cost  of  erecting  plants,  and  it  is  no  uncommon  thing  to  see 
companies  run  through  a  liberal  estimate  of  cash  before  their 
plant  is  near  completion.  Often,  too,  plants  are  turned  over  to 
their  owners  by  the  engineers  erecting  them,  only  for  the  former 
to  find  $50,000  to  $100,000  must  be  spent,  in  order  to  make  the 
changes  necessary  to  a  successful,  economical  operation  of  the 
mill.  Plants  trying  new  machinery,  or  working  with  new  mate- 
rials, can  usually  count  on  doing  a  good  deal  of  altering  on  start- 
ing up ;  and  plants  designed  and  built  by  engineers  inexperienced 
in  the  cement  industry  can  feel  reasonably  sure,  that  the  practical 
man  who  finally  comes  to  their  rescue  will  ask  for  a  very  consid- 
erable sum  of  money  to  put  them  on  an  economical  working  basis. 

I  do  not  believe  any  new  plants  will  be  built  having  kilns  short- 
er than  loo  feet,  and  I  do  not  believe  that  plants  smaller  than  1200 
to  1600  barrels  capacity  can  be  made  to  operate  economically  in 
the  future.  A  plant  of  three  loo-foot  kilns  will  cost  from  $350,- 
ooo  to  $450,000,  exclusive  of  the  cost  of  the  property  and  one  of 
six  loo-foot  kilns  can  probably  be  built  for  from  $600,000  to 
$750,000.  These  estimates  are  of  course  very  general.  They  im- 


COOLING,  GRINDING  AND  STORING  OF  CEMENT  163 

ply  money  well  spent,  with  no  wasting,  and  for  good  machinery. 

Of  the  special  machinery  used  in  a  cement  plant  the  table  below 
gives  the  approximate  price. 

To  this  must  be  added  the  cost  of  foundations  and  erection, 
shafting,  belting,  etc.,  to  run,  etc.,  etc. 

Kiln  (6'  x  60') $3,000.00 

Fire  brick  Lining 300.00 

Kiln  (7'  x  100') 5,000.00 

Fire  brick  lining 600.00 

Kominuter 4,500.00 

Ball  Mill  No.  7 2,800.00 

Ball  Mill  No.  8 3,500.00 

Tube  Mill  (5/6//x22') 3,000.00 

Tube  Mill  (5(x22;) 2,500.00 

Griffin  Mill  ( 30") 2,000.00 

Rock  dryer 2,500.00 

Coal  Dryer  with  brickwork 3,000.00 

Gates  Crusher  No.  5 1,700.00 

Gates  Crusher  No.  6 2,000.00 

Upright  Coolers 2,000.00 

Steel  Storage  Bins  for  Mills  or  Kilns 600.00 

Coal  Bins  with  burning  apparatus 800.00 

Elevators,  each 450  to  600.00 

The  elements  entering  into  the  cost  of  manufacturing  a  barrel 
of  cement  are  as  follows  : 

( r )  Labor. 

(2)  Supplies. 

(a)  Coal  for  burning. 

(b)  Coal  for  power. 

(c)  Gypsum. 

(d)  Limestone  or  clay. 

(e)  Repair  parts. 

(f)  Lubricants. 

(g)  Miscellaneous. 

(3)  Administrative. 

(a)  Mill  office. 

(b)  General  office. 

(c)  Laboratory. 

(4)  Fixed  charges. 

(a)  Interest  on  Bonds,  if  any. 

(b)  Value  of  raw  materials  used. 

(c)  Insurance  and  taxes. 

(d)  Depreciation  of  mill  buildings  and  machinery. 


164  PORTLAND   CEMENT 

The  cost  of  labor  varies  very  greatly  in  different  sections  of  the 
country.  The  cost  of  unskilled  labor  can  of  course  be  estimated 
fairly  well  by  any  one  familiar  with  the  local  conditions.  In  gen- 
eral it  may  be  said  that  a  1200  to  1600  barrel  mill  will  require  one 
unskilled  laborer  for  every  12  to  18  barrels  of  cement  produced. 
Of  the  skilled  laborers  there  will  be  needed  a  quarry  foreman, 
drillers,  millers,  burners,  engineers,  firemen,  packers,  mill 
foremen,  machinists  on  repair  work,  blacksmiths,  etc.  Of 
these  the  millers,  burners,  packers,  mill  foremen  and  some 
of  the  machinists  must  be  experienced  in  cement  mill  work, 
and  consequently  a  new  mill,  located  in  a  new  section  must 
import  these  men  from  one  of  the  old  established  centres  of 
the  industry  and  in  order  to  induce  these  men  to  leave  their  homes 
must  pay  them  much  higher  wages  than  the  older  mills  do.  In 
the  east  the  usual  charge  for  all  labor  (skilled  about  $2.5O-$3.oo. 
Unskilled,  $i.io-$i.5o)  is  between  15  and  20  cents  per  barrel. 

Of  the  supplies,  coal,  gypsum  and  limestone  (or  clay)  can  of 
course  be  calculated  fairly  closely.  Under  favorable  conditions, 
such  as  soft  raw  material  and  a  well  installed  power  generation 
and  transmission  system,  a  barrel  of  cement  can  be  made  with  60 
Ibs.  of  coal ;  and  even  hard  raw  materials  should  not  increase  this 
to  more  than  75  Ibs.  Poor  engines  and  boilers  and  faulty  power 
transmission,  however,  may  easily  raise  this  much  higher.  For 
the  amount  of  coal  used  to  burn  see  the  chapter  on  burning. 

Each  barrel  of  Portland  cement  has  added  to  it  from  8  to  12 
Ibs.  of  gypsum.  The  latter  is  the  limit  placed  by  the  standard 
specifications  and  the  former  is  the  usual  amount  used.  If  plas- 
ter of  Paris  is  used  in  place  of  gypsum  practically  the  same 
amount  is  required  and  its  cost  delivered  is  usually  about  twice  as 
great. 

The  cost  of  lubricants  varies  greatly,  but  under  good  manage- 
ment and  careful  attention  to  avoid  waste,  can  be  reduced  to  from 
0.7  to  I  cent  per  barrel. 

The  repair  parts  form  one  of  the  heaviest  of  the  supply  items 
of  a  cement  mill  and  depend  of  course  largely  on  the  type  of 
machinery  installed  to  do  the  grinding.  The  Griffin  mill  probably 
costing  more  to  keep  in  repairs  than  tube  mills.  The  care  with 


COOLING,  GRINDING  AND  STORING  OF  CEMENT  165 

which  the  machinery  is  used  also  has  a  large  influence  on  this 
item.  Repair  parts  may  cost  anywhere  from  6  to  10  cents  a  bar- 
rel, even  with  good  management. 

The  miscellaneous  supplies  usually  foot  up  to  about  I  to  2  cents 
a  barrel — dynamite  forming  one  of  the  heaviest  items  of  this. 
Theoretically,  the  container  in  which  cement  is  shipped  is  sup- 
posed to  pay  for  itself  and  is  not  included  in  the  cost  of  mill  sup- 
plies. The  labor  of  packing  has  been  included  under  labor. 

The  administration  expenses  vary  greatly  with  the  size  of  the 
mill,  and  the  calibre  of  the  men  employed.  With  a  small  mill  em- 
ploying a  first-class  manager  and  chemist  and  good  assistants, 
this  may  figure  as  high  as  6  cents  a  barrel,  while  a  large  mill  may 
reduce  this  easily  to  2  or  3  cents  a  barrel. 

Of  the  fixed  charges,  taxes  and  insurance  usually  amount  to  I 
to  2  cents  a  barrel.  The  depreciation  of  mill  buildings  and  ma- 
chinery are  usually  figured  at  10%  of  their  cost  erected,  and 
the  interest  on  bonds,  etc.,  can  of  course  be  calculated  with  cer- 
tainty. To  calculate  the  value  of  the  raw  materials  used,  it  is  nec- 
essary to  know  the  amount  of  these  available,  when  the  calculation 
becomes  merely  one  for  arithmetic. 

The  cost  of  manufacturing  Portland  cement  may  therefore  be 
said  to  depend  on  (i)  the  location  of  the  mill  and  the  ease  with 
which  it  can  obtain  its  supplies,  (2)  the  cost  of  labor,  (3)  the 
efficiency  of  the  machinery  installed,  (4)  the  extent,  suitability 
and  softness  of  the  raw  materials,  and  (5)  the  management  and 
running  of  the  mill,  and  the  purchasing  of  its  supplies. 


ANALYTICAL  METHODS. 

CHAPTER   IX. 


THE  ANALYSIS  OF  CEMENT. 


SAMPLING. 

The  knowledge  usually  sought  by  a  chemical  analysis  of  ce- 
ment is  the  average  composition  of  a  given  lot  or  bin.  In  order 
that  it  shall  give  this,  it  is  necessary  that  the  small  sample  used 
in  the  analysis  shall  fairly  represent  the  whole  quantity,  possibly 
many  tons.  In  a  large  lot  of  cement,  it  is  hardly  probable  that  a 
small  sample,  or  even  a  large  sample,  taken  from  one  place  in  the 
bin  or  barrel  in  the  consignment,  will  have  the  average  composi- 
tion of  the  cement,  since  this  particular  point  in  the  bin,  or  this 
special  barrel,  might  be  better  or  worse  than  the  remainder.  It 
is  well  in  sampling  from  a  bin,  to  take  small  samples  from  various 
points,  not  merely  upon  the  surface  where  the  cement  may  have 
become  slightly  altered  by  exposure  to  air  or  damp,  but  also  un- 
derneath by  using  a  fairly  long  brass  tube,  or  some  other  form  of 
sampler,  such  as  will  be  described  hereafter. 

In  sampling  shipments  it  is  best  to  take  a  sample  from  ten  or 
more  bags  or  barrels  in  each  one  hundred  barrels.  Cement1  in 
barrels  should  be  sampled  through  a  hole  made  in  the  centre  of 
one  of  the  staves,  midway  between  the  heads,  or  in  the  head,  by 
means  of  an  auger  or  sampling  iron,  similar  to  that  used  by  sugar 
inspectors.  If  in  bags  it  should  be  taken  from  surface  to  center. 
The  sample  is  then  usually  placed  in  a  clean  paper  bag  or  a  tin 
bucket,  labeled,  and  carried  to  the  laboratory.  Here  the  sample 
is  well  mixed  by  passing  several  times  through  a  coarse  sieve, 
and  by  rolling  back  and  forth  on  a  sheet  of  paper,  or  better  still, 
one  of  oil  cloth.  When  thoroughly  well  mixed  it  is  spread  out 
in  a  thin  layer  on  the  paper,  or  oil  cloth,  and  divided  into  20  to 
30  little  squares  with  the  points  of  a  spatula  or  trowel.  A  small 
quantity  (about  2  or  3  grams)  of  cement  is  now  taken  from  each 

1  Committee  on  Uniform  Tests,  Am.  Soc.  C.  K. 


ANALYTICAL  METHODS  1 67 

one  of  these  squares  with  the  trowel  or  spatula  point  and  these 
small  samples  are  mixed  and  ground  for  the  chemical  analysis. 
The  main  portion  of  the  cement  is  then  replaced  in  the  bag  or 
bucket  and  used  for  the  physical  tests. 

In  order  that  the  solvents  used  to  decompose  the  cement  for 
analysis  may  do  their  work,  the  portion  weighed  out  must  con- 
tain no  coarse  pieces  of  clinker.  To  guard  against  this,  pass  the 
smaller  sample  through  a  No.  loo-mesh  test  sieve,  grinding  any 
residue  caught  upon  the  sieve  in  an  agate  mortar  until  it,  too, 
passes.  From  the  size  and  shape  of  the  ordinary  agate  mortar 
and  pestle  the  operation  of  grinding  is  very  fatiguing.  It  may  be 
much  facilitated,  however,  by  cutting  a  hole,  of  such  size  and 
shape  as  to  hold  the  mortar  firmly,  in  the  middle  of  a  block  of 
hard  wood,  a  foot  or  so  square.  The  pestle  is  then  fixed  in  a 
piece  of  round  brass  tubing  of  sufficient  bore,  or  else  in  a  round 
hard  wood  handle.  Several  mechanical  grinders  are  on  the  mar- 
ket, descriptions  of  which  may  be  found  in  the  trade  catalogues 
of  most  of  the  prominent  dealers  in  chemical  apparatus. 

After  being  ground  the  sample  for  chemical  analysis  should  be 
placed  in  a  small  (one  or  two  ounce)  wide  mouth  bottle  and  tight- 
ly corked.  If  for  immediate  use  a  sample  or  coin  envelope  may 
be  substituted  for  the  bottle.  The  bottles  are  cheap  enough,  how- 
ever, and,  as  cement  rapidly  absorbs  water  and  carbon  dioxide 
from  the  air,  it  is  a  good  rule  to  use  them  altogether. 

Samplers. 

In  sampling  cement  from  a  bag  or  barrel  a  small  brass  tube 
with  a  slit  cut  down  the  middle  may  be  used.  The  slit  is  neces- 
sary as  the  cement  becomes  packed  in  the  tube  when  it  is  thrust 
into  the  cement  and  it  is  necessary  to  run  a  lead  pencil  or  nail  up 
and  down  the  opening  to  get  the  cement  out.  The  tube  for  this 
purpose  need  not  be  over  two  feet  long  and  its  upper  end  should 
be  screwed  into  a  T,  the  latter  forming  a  handle.  The  forms  of 
grain  and  sugar  samplers  sold  by  dealers  in  apparatus  for  cement 
testing  may  be  used  also  for  sampling  bags  and  barrels. 

For  sampling  bins  of  cement  in  the  stock  houses  at  the  mill  the 
depth  of  the  former,  often  eight  or  more  feet,  makes  their  proper 
sampling  a  difficult  matter  unless  a  specially  devised  sampling  rod 


1 68 


PORTLAND  CEMENT 


is  at  hand.  In  order  to  get  an  average  of  the  bin  it  is  necessary 
to  draw  portions  from  it  at  all  depths  and  at  both  ends.  The 
best  form  of  apparatus  which  the  writer  has  seen  for  doing  this, 
consists  of  a  long  iron  rod  such  as  is  shown  in  Fig.  38. 


D  O  /] 


LJ 

Fig.  38     Jointed  Sampling  Rod. 

It  is  made  of  I  inch  wrought  iron  piping  and  in  sections  of 
about  four  feet  each,  to  allow  of  its  being  readily  carried  about 
from  one  mill  to  another.  The  couplings  are  long  and  are  turned 
down  so  as  to  taper  at  either  end.  In  the  end  of  the  rod  is  fastened 
a  steel  point  and  slots  about  }/2.  inch  in  width  and  fourteen  inches 
in  length  are  cut  in  each  section  as  shown  in  the  illustration.  One 
side  of  each  slot  is  made  to  project  slightly  beyond  the  side  of 
the  pipe  and  sharpened,  as  shown  in  the  section  A-B.  In  using 
the  rod,  as  many  sections  are  used  as  may  be  necessary  to  reach 
to  the  bottom  of  the  bin.  These  are  joined,  the  whole  is  thrust 
into  the  bin  until  it  reaches  the  bottom,  the  rod  is  filled  by  turn- 
ing it  a  few  times,  then  withdrawn,  turned  upside  down  and  the 
cement  shaken  out  of  it  into  a  bag  by  rapping  it  against  the  side 
of  the  stock  house. 

A  rod  made  with  the  slot  running  its  entire  length  and  termi- 
nating in  a  T,  with  two  pieces  of  short  pipe  screwed  into  it  to  form 
a  handle,  is  sometimes  used  to  sample  bins.  The  main  trouble 
with  this  rod  is  that  such  a  long  slot  weakens  the  sampler,  and 


ANALYTICAL  METHODS 


169 


unless  made  of  very  heavy  pipe  it  soon  twists  out  of  shape.  Grain 
samplers  may  also  he  used  to  sample  bins,  but  are  seldom  made 
long  enough  to  reach  the  bottom  of  the  bins. 

A  vacuum  sampling  apparatus  invented  by  Bertram  Blount, 
the  English  cement  expert,  is  described  in  THE:  CHEMICAL  ENGI- 
NEER, January,  1905,  p.  161,  which  consists  first  of  a  small  iron 
pipe  some  jHHnch  in  bore,  with  one  end  closed  and  drawn  to  a 
point.  The  other  end  is  open,  and  to  it  can  be  attached  a  length 
of  rubber  tubing.  The  pointed  end  of  the  pipe  has  a  number  of 
small  holes  pierced  in  it,  and  to  take  a  sample  this  tube  is  thrust 
into  the  heap  of  cement.  It  may  be  pushed  in  at  any  angle  from 
vertical  downwards.  The  india-rubber  tube  above  referred  to  is 


Fig.  59,  Blouiit's  Vacuum  Sampler. 

connected  to  a  drum  provided  with  an  opening  covered  with  a 
screw  cap,  the  whole  being  made  air-tight.  The  apparatus  is 
completed  by  means  of  an  exhausting  pump  which  may  either  be 
worked  by  hand  or  by  a  small  motor.  It  is  also  connected  to  the 
drum  by  a  length  of  rubber  tubing.  Each  length  of  rubber  tub- 
ing is  provided  with  a  screw  slip,  which  can  be  made  to  nip  the 
tubing  so  tightly  that  no  air  can  get  past 

In  sampling  the  iron  pipe  is  plunged  nearly  to  the  bottom  of  the 
cement.    The  amount  of  cement  which  is  forced  through  the  small 


I7O  PORTLAND  CEMENT 

holes  in  the  lower  end  of  the  pipe  during  this  process  is  so  small 
that  it  may  be  neglected.  The  clip  on  the  rubber  tube  joining  the 
sampling  pipe  with  the  drum  is  then  screwed  up.  A  man  then 
worked  the  pump,  and  exhausts  the  drum  until  a  vacuum  equal  to 
some  18  or  20  inches  of  mercury  has  been  produced,  when  the 
clip  on  the  tube  between  the  drum  and  the  pump  is  screwed  up. 
The  drum  has  fitted  to  it  a  gauge,  so  that  the  amount  of  vacuum 
in  it  may  be  readily  seen.  The  clip  on  the  tube  between  the  samp- 
ling pipe  and  the  reservoir  drum  is  then  unscrewed,  with  the  re- 
sult that  a  certain  amount  of  cement  will  be  drawn  through  the 
small  holes  in  the  sampling  pipe,  up  through  the  latter,  and  then 
conveyed  thence  through  the  rubber  tube  to  the  reservoir.  The 
whole  process  takes  but  a  minute  or  two,  and  the  amount  drawn 
into  the  reservoir  varies  with  the  vacuum  produced.  Several 
samples  may  be  taken  if  desirable,  and  the  whole  operation  re- 
quires but  half  an  hour. 


DETERMINATION  OF  SILICA,  FERRIC  OXIDE  AND 
ALUMINA,  LIME  AND  MAGNESIA. 

Method  Proposed  by  the  Committee  on  Uniformity  in  the  Analy- 
sis of  Materials  of  the  Portlond  Cement  Industry  of  the  New 
York  Section  of  the  Society  of  Chemical  Industry*1 

Solution. 

One-half  gram  of  the  finely  powdered  substance  is  to  be 
weighed  out  and,  if  a  limestone  or  unburned  mixture,  strongly 
ignited  in  a  covered  platinum  crucible  over  a  strong  blast  for  15 
minutes,  or  longer  if  the  blast  is  not  powerful  enough  to  effect 
complete  conversion  to  a  cement  in  this  time.  It  is  then  trans- 
ferred to  an  evaporating  dish,  preferably  of  platinum  for  the  sake 
of  celerity  in  evaporation,  moistened  with  enough  water  to  pre- 
vent lumping,  and  5  to  10  cc.  of  strong  HC1  added  and  digested 

1  This  committee  consisted  of  Messrs.  Clifford  Richardson,  .Spencer  B.  Newberry  and 
H.  A.  Schaffer.  Their  various  reports  were  published  injournal  of  the  Society  of  Chemical 
Industry,  XXI,  12,  830  and  1216  ;  Journal  American  Chemical  Society,  XXV.  1180  and  XXVI 
995  ;  and  Cement  and  Engineering  News  XVI,  37. 


ANALYTICAL  METHODS  17! 

with  the  aid  of  gentle  heat  and  agitation  until  solution  is  com- 
plete. Solution  may  be  aided  by  light  pressure  with  the  flattened 
end  of  a  glass  rod.1  The  solution  is  then  evaporated  to  dryness, 
as  far  as  this  may  be  possible  on  the  bath. 

Silica. 

The  residue  without  further  heating  is  treated  at  first  with  5 
to  10  cc.  of  strong  HC1  which  is  then  diluted  to  half  strength  or 
less,  or  upon  the  residue  may  be  poured  at  once  a  larger  volume 
of  acid  of  half  strength.  The  dish  is  then  covered  and  digestion 
allowed  to  go  on  for  10  minutes  on  the  bath,  after  which  the  solu- 
tion is  filtered  and  the  separated  silica  washed  thoroughly  with 
water.  The  filtrate  is  again  evaporated  to  dryness,  the  residue 
without  further  heating,  taken  up  with  acid  and  water  and  the 
small  amount  of  silica  it  contains  separated  on  another  filter 
paper.  The  papers  containing  the  residue  are  transferred  wet  to 
a  weighed  platinum  crucible,  dried,  ignited,  first  over  a  Bunsen 
burner  until  the  carbon  of  the  filter  is  completely  consumed,  and 
finally  over  the  blast  for  15  minutes  and  checked  by  a  further 
blasting  for  10  minutes  or  to  constant  weight.  The  silica,  if  great 
accuracy  is  desired,  is  treated  in  the  crucible  with  about  10  cc. 
of  HF1  and  four  drops  of  H2SO4  and  evaporated  over  a  low 
flame  to  complete  dryness.  The  small  residue  is  finally  blasted, 
for  a  minute  or  two,  cooled  and  weighed.  The  difference  be- 
tween this  weight  and  the  weight  previously  obtained  gives  the 
amount  of  silica.1 

Al2Oo  and  Fe2Oz, 

The  filtrate,  about  250  cc.,  from  the  second  evaporation  for 
SiO2,  is  made  alkaline  with  NH4OH  after  adding  HC1,  if  need 
be,  to  insure  a  total  of  10  to  15  cc.  strong  acid,  and  boiled  to  ex- 
pel excess  of  NH3,  or  until  there  is  but  a  faint  odor  of  it,  and  the 
precipitated  iron  and  aluminum  hydrates,  after  settling,  are 
washed  once  by  decantation  and  slightly  on  the  filter.  Setting 
aside  the  filtrate,  the  precipitate  is  dissolved  in  hot  dilute  HC1, 
the  solution  passing  into  the  beaker  in  which  the  precipitation 

1  If  anything  remains  undecomposed  it  should  be  separated,  fused  with  a  little  Na2 
CO2  dissolved  and  added  to  the  original  solution.  Of  course  a  small  amount  of  separated 
non-gelatinous  silica  is  not  to  be  mistaken  for  undecomposed  matter. 

1  For  ordinary  control  work  in  the  plant  laboratory  this  correction  may,  perhaps,  be 
neglected  ;  the  double  evaporation  never. 


172  PORTLAND   CEMENT 

was  made.  The  aluminum  and  iron  are  then  reprecipitated  by 
NH4OH,  boiled  and  the  second  precipitate  collected  and  washed 
on  the  same  filter  used  in  the  first  instance.  The  filter  paper, 
with  the  precipitate,  is  then  placed  in  a  weighed  platinum  cruci- 
ble, the  paper  burned  off  and  the  precipitate  ignited  and  finally 
blasted  5  minutes,  with  care  to  prevent  reduction,  cooled  and 
weighed  as  A12O3  +  Fe2O3.2 

CaO. 

To  the  combined  filtrate  from  the  A12O3  +  Fe2O3  precipitate  a 
few  drops  of  NH4OH  are  added,  and  the  solution  brought  to 
boiling.  To  the  boiling  solution  20  cc.  of  a  saturated  solution  of 
ammonium  oxalate  are  added,  and  the  boiling  continued  until  the 
precipitated  CaC2O4  assumes  a  well-defined  granular  form.  It 
is  then  allowed  to  stand  for  20  minutes,  or  until  the  precipitate 
has  settled,  and  then  filtered  and  washed.  The  precipitate  and 
filter  are  placed  wet  in  a  platinum  crucible,  and  the  paper  burned 
off  over  a  small  flame  of  a  Bunsen  burner.  It  is  then  ignited,  re- 
dissolved  in  HC1,  and  the  solution  made  up  to  100  cc.  with  water. 
Ammonia  is  added  in  slight  excess,  and  the  liquid  is  boiled.  If 
a  small  amount  of  A12O3  separates  this  is  filtered  out,  weighed, 
and  the  amount  added  to  that  found  in  the  first  determination, 
when  greater  accuracy  is  desired.  The  lime  is  then  reprecipitated 
by  ammonium  oxalate,  allowed  to  stand  until  settled,  filtered, 
and  washed.3  weighed  as  oxide  by  ignition  and  blasting  in  a  cov- 
ered crucible  to  constant  weight,  or  determined  with  dilute  stand- 
ard permanganate.4 

MgO. 

The  combined  filtrates  from  the  calcium  precipitates  are  acid- 
ified with  HC1  and  concentrated  on  the  steam-bath  to  about  150 
cc.,  10  cc.  of  saturated  solution  of  Na(NH4)HPO4  are  added, 
and  the  solution  boiled  for  several  minutes.  It  is  then  removed 
from  the  flame  and  cooled  by  placing  the  beaker  in  ice  water. 
A-fter  cooling,  NH4OH  is  added  drop  by  drop  with  constant  stir- 
ring until  the  crystalline  ammonium-magnesium  ortho-phosphate 

2  This  precipitate  contains  TiO2.  Po0.-,.  MnsO4. 

a  The  volume  of  wash  water  should  not  be  too  large  ;  vide  Hillebrand. 
4  The  accuracy  of  this  method  admits  of  criticism,  but  its  convenience  and  rapidity  de- 
mand its  insertion. 


ANALYTICAL  METHODS  173 

begins  to  form,  and  then  in  moderate  excess,  the  stirring  being 
continued  for  several  minutes.  It  is  then  set  aside  for  several 
hours  in  a  cool  atmosphere  and  filtered.  The  precipitate  is  re- 
dissolved  in  hot  dilute  HC1,  the  solution  made  up  to  about  100 
cc.,  i  cc.  of  a  saturated  solution  of  Na(NH4)HPO4  added,  and 
ammonia  drop  by  drop,  with  constant  stirring  until  the  precipitate 
is  again  formed  as  described  and  the  ammonia  is  in  moderate  ex- 
cess. It  is  then  allowed  to  stand  for  about  2  hours  when  it  is 
filtered  on  a  paper  or  a  Gooch  crucible,  ignited,  cooled  and  weigh- 
ed as  Mg2P2O7. 

Method  Proposed  by  the  Committee  on  the  Uniform  Analysis  of 

Cement  and  Cement  Materials  of  the  Lehigh  Volley  Section 

of  the  American  Chemical  Society*1 

Weigh  out  .5  gram  into  a  wide  platinum  dish  of  about  50  cc. 
capacity ;  add  a  very  little  water  and  break  up  lumps  with  a  glass 
rod;  add  5  cc.  hydrochloric  acid  (i-i)  and  evaporate  to  dryness 
at  a  moderate  heat,  continuing  to  heat  the  mass — not  above  200° 
C. — until  all  odor  of  acid  is  gone.  Do  not  hurry  this  baking  or 
skimp  the  time.  The  whole  success  of  the  analysis  depends  on 
thoroughness  at  this  point.  Cool;  add  20  cc.  hydrochloric  acid 
(i-i)  ;  cover  and  boil  gently  for  ten  minutes;  add  30  cc.  water, 
raise  to  boiling,  and  filter  off  the  silica ;  wash  with  hot  water  four 
or  five  times;  put  in  crucible,  ignite  (using  blast  for  10  minutes), 
and  weigh  as  SiO2. 

Iron  and  Alumina. 

Make  filtrate  alkaline  with  ammonia,  taking  care  to  add  only 
slight  excess ;  add  a  few  drops  of  bromine  water  and  boil  till 
odor  of  ammonia  is  faint.  Filter  off  the  hydroxides  of  iron  and 
aluminum,  washing  once  on  the  filter.  Dissolve  the  precipitate 
with  hot  dilute  nitric  acid,  reprecipitate  with  ammonia ;  boil  five 
minutes ;  filter  and  wash  the  iron  and  alumina  with  hot  water 
once ;  place  in  crucible,  ignite  carefully,  using  blast  for  5  min- 
utes, and  weigh  combined  iron  and  aluminum  oxides. 

i  This  committee  was  appointed  at  a  meeting  of  the  L,ehigh  Valley  Section  of  the  Amer- 
ican Chemical  Society,  held  November  18,  1903,  and  consisted  of  Messrs.  Wm.  B.  Newberry 
Richard  K.  Meade  and  Ernest  B.  McCready.  Their  report  was  published  in  Cement  and 
EHi^iiftTuix  News,  August,  1904,  and  embodies  the  methods  most  acceptable  to  the 
chemists  actively  employed  in  the  cement  industry  as  ascertained  by  correspondence 
with  the.se  chemists  themselves. 


174  PORTLAND  CEMENT 

Lime. 

Make  the  filtrate  from  the  hydroxides  alkaline  with  ammonia; 
boil;  add  20  cc.  boiling  saturated  solution  ammonium  oxalate; 
continue  boiling  for  five  minutes ;  let  settle  and  filter.  Wash  the 
calcium  oxalate  thoroughly  with  hot  water  using  not  more  than 
125  cc.,  and  transfer  it  to  the  beaker  in  which  it  was  precipitated, 
spreading  the  paper  against  the  side  and  washing  down  the  pre- 
cipitate first  with  hot  water  and  then  with  dilute  sulphuric  acid 
(1-4);  remove  paper;  add  50  cc.  water,  10  cc.  cone,  sulphuric 
acid,  heat  to  incipient  boiling  and  titrate  with  permanganate1,  cal- 
culating the  CaO. 

Magnesia. 

If  the  filtrate  from  the  calcium  oxalate  exceeds  250  cc.,  acidify, 
evaporate  to  that  volume;  cool,  and  when  cold  add  15  cc.  strong 
ammonia  and  with  stirring  15  cc.  stock  solution  of  sodium  hy- 
drophosphate.  Allow  to  stand  in  the  cold  six  hours  or  prefer- 
ably over  night;  filter;  wash  the  magnesium  phosphate  with  di- 
lute ammonia  (1-4+  100  gms.  ammonium  nitrate  per  litre)  put 
in  crucible,  ignite  at  low  heat  and  weigh  the  magnesium  pyro- 
phosphate. 

NOTES. 

Of  the  above  schemes,  the  first  is  undoubtedly  the  more  accu- 
rate of  the  two.  It  does  not  seem  practicable,  however,  to  use  it 
in  the  everyday  routine  work  of  the  mill  laboratory.  It  also  re- 
quires a  rather  high  degree  of  manipulative  skill  to  carry  out  the 
additional  steps  in  its  performance.  When  very  accurate  deter- 
minations are  required,  it  will  undoubtedly  give  better  results 
than  the  second  scheme,  provided  the  analysis  is  skilfully  execu- 
ted. On  the  other  hand,  under  the  conditions  usually  met  with 
in  the  laboratories  of  cement  manufacturers  and  large  users, 
where  rapidity,  coupled  with  a  moderate  degree  of  accuracy  is  re- 
quired, and  where  one  man  is  required  to  run  a  number  of  analy- 
ses per  day,  the  second  scheme  will  unquestionably  give  more  sat- 
isfaction, if  properly  carried  out. 

A  good  well-made  Portland  cement  is  practically  entirely  soluble 
in  hydrochloric  acid.     Fusion,  therefore,  with  sodium  or  potas- 

1  See  "Volumetric  Determination  of  Lime,"  page  185. 


ANALYTICAL  METHODS  175 

sium  carbonate  is  rarely  necessary.  It  is  also  objectionable,  for 
when  calcium  and  magnesium  are  precipitated,  as  oxalate  and 
phosphate  respectively,  from  solutions  containing  much  sodium 
or  potassium  salts,  the  precipitates  are  almost  sure  to  be  contami- 
nated with  alkaline  salts.  Even  much  washing  fails  to  remove 
the  impurity  from  the  precipitate.  When,  therefore,  the  sample 
of  cement  has  been  fused  directly  with  from  3  to  5  grams  of 
sodium  carbonate,  there  is  sure  to  be  this  danger  that  the  lime 
and  magnesia  precipitates  will  carry  down  some  sodium  salts, 
from  which  subsequent  washing  will  fail  to  free  them.  In  accu- 
rate work  this  error  can  be  eliminated  by  reprecipitation.  If  in- 
stead of  fusing  the  sample  directly  with  five  to  ten  times  its 
weight  of  sodium  carbonate,  the  impure  silica,  separated  by  treat- 
ment with  hydrochloric  acid,  is  fused  with  an  equal  bulk  of 
sodium  carbonate,  the  quantity  of  sodium  salts  introduced  into 
the  solution  will  be  reduced  to  one-fourth,  -usually  between  i.o 
and  1.5  gram  of  sodium  chloride.  , 

Should  the  cement  prove  to  leave  a  considerable  residue  of  sili- 
cious  matter  on  dissolving  in  acid,  the  best  plan  will  be  to  weigh 
out  a  new  sample  and  pursue  the  following  method  suggested  by 
Dr.  Porter  W.  Shinier,  Easton,  Pa. : 

Weigh  l/2  gram  of  the  finely  ground  dried  cement  into  a  plati- 
num crucible  and  mix  intimately,  by  stirring  with  a  glass  rod, 
with  0.5  gram  of  pure  dry  sodium  carbonate.  Brush  off  the  rod 
into  the  crucible  with  a  camel's  hair  brush.  Cover  the  crucible 
and  place  over  a  low  flame.  Gradually  raise  the  flame  until  the 
crucible  is  red  hot  and  continue  the  heating  for  five  minutes 
longer ;  then  place  over  a  blast  lamp  and  heat  five  minutes  more. 
While  still  hot,  plunge  the  bottom  of  the  crucible  half  the  way  up 
into  cold  water.  This  will  loosen  the  mass.  Drop  the  mass  into 
a  casserole  or  dish  and  cover  the  latter  with  a  watch  glass.  Pour 
into  the  crucible  a  portion  of  a  mixture  of  30  cc.  of  hot  water  and 
10  cc.  of  dilute  hydrochloric  acid.  Heat  on  a  hot  plate,  and  then 
pour  into  the  dish  or.  casserole.  Clean  out  the  crucible  with  a 
rubber-tipped  rod,  using  the  rest  of  the  acid  and  water.  The 
quantity  of  sodium  salts  introduced  into  the  solution  from  0.5 
gram  of  carbonate  is  so  small  that  possible  contamination  of  the 
lime  and  magnesia  precipitates  is  done  away  with.  On  heat. 


176  PORTLAND  CEMENT 

ing  cement  and  sodium  carbonate  together  in  this  proportion  no 
fusion  takes  place,  only  a  sintering. 

Some  operators1  make  the  amount  of  residue  left  on  solution 
with  acid  a  test  of  the  thoroughness  with  which  the  cement  has 
been  made.  Peckham  uses  a  10  per  cent,  solution  of  hydrochloric 
acid  and  5  grams  of  cement  just  as  received,  making  the  solution 
slowly  and  with  care.  Blount  dissolves  the  cement  in  strong  hy- 
drochloric acid,  evaporates  the  solution  to  dryness,  but  not  inten- 
tionally baking  the  evaporated  material,  redissolving  in  hydro- 
chloric acid,  filters,  washes,  dissolves  the  precipitated  silica  with 
sodium  carbonate  solution  and  collects,  ignites  and  weighs  the 
final  insoluble  residue. 

If  this  test  is  to  be  made  use  of  to  check  the  burning  and 
proper  grinding  and  mixing  of  the  raw  materials  the  process  of 
Blount  is  more  nearly  correct,  since  it  is  not  effected  so  much  by 
the  conditions  under  which  solution  is  effected.  The  quantity 
of  silica  which  will  be  left  on  treating  cement  with  acid  will  de- 
pend not  only  upon  the  chemical  composition  of  the  cement,  but 
also  upon  the  fineness  to  which  the  sample  is  ground,  strength  of 
acid,  etc.  Coarsely  ground  material  giving  much  more  residue 
than  finely  ground.  Cement  passing  a  5<>mesh  sieve,  but  retained 
by  a  100,  will  give  much  more  silica  than  that  passing  a  100- 
mesh,  but  retained  on  a  2OO-mesh,  yet  neither  has  binding  prop- 
erties in  the  ordinary  sense  of  the  word,  so  that  the  contention 
made  that  the  silica  which  does  not  dissolve  even  though  it  may 
come  from  good  properly  burned  material,  still  comes  from  inert 
particles,  and  is  therefore  not  in  a  form  of  active  combination,  is 
not  logical  because  by  grinding  these  inert  particles  a  little  finer 
we  can  considerably  reduce  the  silica  left  without  increasing  any 
their  hydraulic  value.  Many  silicates  are  also  soluble  in  acid, 
which  have  no  hydraulic  properties,  such  as  slags,  so  that  all  the 
-silica  which  goes  into  solution  is  not  necessarily  combined  in  such 
a  way  as  to  form  hydraulic  compounds. 

The  test  as  applied  by  Blount  does  not  seem  of  much  practical 
value,  either.  Of  course,  when  the  residue  of  uncombined  silica 
is  large,  it  shows  something  is  wrong  with  the  cement,  but  this 

l  Peckham  :  /.  S.  Chem.  Ind.  XXI,  831  and/.  Amer.  Chem.  Soc.  XXVI,  1636  and  Blount 
/.  Am.  Chem.  Soc.  XXVI,  995. 


ANALYTICAL  METHODS  177 

fact  is  usually  revealed  much  more  satisfactorily  by  the  tests  for 
soundness  which  property  is  dependent  on  the  proper  combination 
of  the  silica  with  the  lime.  A  marl  containing  a  per  cent,  or  so 
of  silica  in  the  form  of  quartz  grains  wovild  probably  give  a  ce- 
ment containing  from  ]/2  to  i  per  cent,  of  insoluble  or  uncombined 
silica,  yet  if  this  quartz  had  been  taken  into  consideration  in  pro- 
portioning the  raw  materials,  this  cement  might  easily  be  better 
than  one  which  gives  no  free  or  uncombined  silica,  because  the 
latter  might  be  unsound.  Also,  as  we  have  said  before,  all  the 
silica,  which  is  reported  as  combined  is  not  necessarily  so  combin- 
ed as  to  form  Portland  cement. 

At  the  mill  itself,  there  is  little  knowledge  to  be  gained  by  the 
test  as  used  by  either  Peckham  or  Blount,  as  the  soundness  test, 
coupled  with  the  usual  determinations,  will  tell  us  whether  the 
fault  is  due  to  faulty  manufacture  or  improper  proportioning  of 
the  raw  materials. 

Alex.  Cameron,1  in  1894,  pointed  out  the  fact  that  no  matter 
how  many  evaporations  were  made  in  determining  silica,  accu- 
rate results  could  not  be  obtained  unless  a  filtration  intervened 
between  each  one.  This  paper  seems  to  have  escaped  the  notice 
of  most  chemists  and  was  only  brought  to  their  knowledge  by 
Dr.  W.  F.  Hillebrand,2  in  1901,  in  a  paper  read  at  a  meeting  of 
The  American  Chemical  Society,  in  Philadelphia,  in  December  of 
that  year,  in  which  he  gave  the  results  of  his  own  experiments 
along  that  line.  It  was  in  accordance  with  his  suggestion  that  the 
committee  of  the  New  York  Section  of  the  Society  of  Chemical 
Industry  advised  the  double  evaporation  with  intervening  filtra- 
tion, which  they  inserted  in  their  scheme.  There  is  no  question 
but  that  Dr.  Hillebrand  is  right  and  that  this  procedure  is  neces- 
sary in  very  accurate  work.  In  the  analysis  of  Portland  cement, 
a  residue  of  silica,  amounting  to  from  two  to  four  milligrams, 
can  usually  be  obtained  by  evaporation  of  the  filtrate  from  the 
first  silica  precipitate  to  dryness,  still  the  extra  step  is  tedious, 
and  adds  considerably  to  the  time  necessary  for  making  an  analy- 
sis. It  is  also  true,  however,  that  there  is  considerable  iron  and 
alumina  carried  down  with  the  silica,  and  that  these  two  errors 

1  Jour.  Anier.  Chem.  Sec.  XXIV,  362. 
Chem.  AVa/j,I«XIX,  171. 


178 


PORTLAND   CEMENT 


will  balance  each  other  to  a  great  extent,  so  that  the  amount  of 
silica  reported  is  seldom  more  than  one  or  two-tenths  of  a  per 
cent.  low.  Below  are  some  figures  upon  this. 


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Silica  is  hard  to  wash  and  retains  alkalies  tenaciously.  It  is  well 
for  the  inexperienced  operator,  until  he  finds  out  how  much  wash- 
ing is  required,  to  test  with  silver  nitrate,  and  continue  the  opera- 
tion until  the  washings  cease  to  react  for  chlorides. 

Silica  may  be  ignited  wet,  but  care  must  be  taken  not  to  dry 
the  precipitate  too  quickly  over  the  flame,  else  the  steam  in  es- 
caping will  carry  with  it  fine  particles  of  silica.  The  best  plan  is 
not  to  place  the  crucible  at  first  directly  over  the  burner,  but  in- 
stead to  one  side  of  a  low  flame.  The  silica  must  be  ignited  over 
a  blast  lamp  in  order  to  drive  off  the  last  traces  of  water,  which 
it  holds  most  tenaciously.  Ignition  over  a  Bunsen  burner,  even  for 
some  hours,  is  insufficient  for  complete  dehydration.  The  blast 
lamp  will  also  help  to  burn  off  the  last  trace  of  the  carbon  of  the 
filter  paper. 

The  purity  of  the  silica  can  easily  be  tested,  and  indeed  in 

1  This  represents  the  silica  which  would  be  found  by  the  method  of  the  committee  of 
the  L,ehigh  Valley  Section  of  the  American  Chemical  Society. 

2  This  represents  the  silica  actually  present  in  the  sample. 


ANALYTICAL  METHODS  179 

accurate  work,  it  should  always  be  done.  After  burning  off  the 
carbon,  igniting  over  a  blast  and  accurately  weighing,  moisten 
the  silica  with  dilute  sulphuric  acid  and  then  half  fill  the  crucible 
with  C.  P.  hydrofluoric  acid.  Incline  the  crucible  on  a  tripod 
over  a  burner  turned  low,  in  such  a  way  that  the  flame  plays 
under  the  upper  part  of  the  crucible.  This  causes  a  rapid  evapo- 
ration of  the  solution.  When  no  more  fumes  come  from  the  cru- 
cible move  the  burner  back  until  it  plays  upon  the  bottom  of  the 
crucible  and  raise  the  flame  until  the  crucible  is  cherry-red.  Cool 
and  weigh.  The  loss  represents  silica,  SiO2,  and  the  residue  in 
the  crucible  is  usually  alumina.  Its  weight  may  be  added  to 
that  of  the  iron  and  alumina  found  by  precipitation  with  am- 
monia, or  the  residue  may  be  dissolved  in  concentrated  hydro- 
chloric acid  and  added  to  the  filtrate  from  the  silica,  before  the 
addition  of  ammonia. 

If  silica  is  to  be  purified,  however,  it  is  also  necessary,  not  only 
to  make  the  double  evaporation  with  intervening  filtration,  but 
also  to  determine  the  silica  in  the  iron  and  alumina  and  add  it  to 
the  weight  of  the  purified  silica.  Unless  this  is  done  the  silica 
will  be  too  low  and  the  iron  and  alumina  too  high. 

Alumina,  A12O3,  is  soluble  to  some  extent  in  a  large  excess  of 
ammonia.  If,  however,  the  excess  is  expelled  by  boiling,  the 
alumina  is  again  precipitated.  The  presence  of  ammonium  chlor- 
ide in  the  solution  greatly  aids  in  the  separation  of  alumina  by  am- 
monia. The  precipitate  of  iron  and  alumina  must  be  filtered  off 
promptly  since  the  alkaline  liquid  will  absorb  carbon  dioxide 
from  the  air,  forming  calcium  carbonate  which  would  be  filtered 
off  with  the  iron  and  alumina.  For  the  same  reason,  when  for 
any  cause  the  filtrate  from  the  iron  and  alumina  has  to  stand 
some  days,  it  should  be  acidified  with  hydrochloric  acid  before 
setting  aside.  This  is  necessary  when  the  calcium  is  to  be  deter- 
mined volumetrically,  and  it  saves  trouble  elsewhere,  since  the 
deposit  of  calcium  carbonate  forms  as  a  crust  on  the  sides  and 
bottom  of  the  beaker,  and  is  very  difficult  to  remove,  without 
solution  and  reprecipitation. 

To  avoid  time  lost  in  boiling  off  a  large  excess  of  ammonia, 
only  a  very  slight  excess  of  this  reagent  should  be  added.  The 


i8o 


PORTLAND  CEMENT 


bottle  shown  in  Fig.  40  will  be  found  very  useful  in  ammonia 
precipitations,  as  the  addition  can  be  made  drop  by  drop,  if  de- 
sired, and  the  quantity  added  regulated  so  as  to  give  the  liquid 
only  a  faint  odor  of  ammonia. 

Magnesium  hydroxide,  Mg(OH)2,  is  not  completely  soluble  in 
ammonia.  The  precipitate  is,  however,  readily  soluble  in  am- 
monia solutions,  containing  sufficient  ammonium  chloride.  The 
precipitation  of  the  magnesia  along  with  the  iron  and  alumina 
is  insured  against  by  the  formation  of  ammonium -chloride,  which 
takes  place  before  the  iron  and  alumina  are  precipitated,  on  add- 
ing ammonia  to  the  hydrochloric  acid  solution.  If  preferable, 
the  operator  can  be  on  the  safe  side  by  adding  half  a  gram  of  the 
salt  itself  (ammonium  chloride)  to  the  filtrate  from  the  silica  be- 
fore precipitating  the  iron  and  alumina.  The  presence  of  am- 
monium chloride  is  also  necessary  for  the  complete  precipitation 
of  the  alumina. 


Fig.  40,  Apparatus  for  Ammonia  Precipitation. 

The  precipitate  of  iron  and  alumina  always  contains  more  or 
less  lime  and  magnesia,  from  which  long  washing  fails  to  free  it. 
Solution  and  reprecipitation  are,  therefore,  necessary  to  get 
around  the  difficulty.  The  precipitate  is  very  apt  to  contain  traces 
of  silica  also.  Some  of  this  comes  from  the  action  of  the  am- 


ANALYTICAL  METHODS  l8l 

monia  on  the  reagent  bottle  in  which  it  is  kept,  some  from  the 
action  of  the  alkaline  liquid  on  the  beaker  in  which  the  precipita- 
tion was  made,  and  some  which  failed  to  be  separated  by  evapora- 
tion in  the  proper  place  is  also  carried  down  here.  Since  the 
impurity  usually  present  in  the  silica  is  alumina  and  that  in  the 
alumina  is  silica,  the  two  sources  of  error  tend  to  balance  each 
other.  If  desired  the  weighed  precipitate  of  ferric  oxide  and 
alumina  can  be  dissolved  by  fusion  with  potassium  bisulphate  for 
some  hours,  the  fused  mass  dissolved  in  water,  a  few  drops  of  sul- 
phuric acid  added  and  the  solution  evaporated  until  fumes  come 
off  in  quantity.  The  residue  is  then  collected  after  cooling  and 
diluting  the  solution,1  and  weighed  as  SiO.2 

Ammonia  water  takes  up  silica  rapidly  from  the  glass  con- 
tainer, hence  when  accurate  work  is  desired  and  purification  of 
silica  and  alumina  are  to  be  undertaken,  it  is  necessary  to  redistill 
the  ammonia  over  lime.  This  should  be  done  every  week  or  two 
at  least.  Even  for  technical  work  it  is  not  a  bad  plan,  as  there  is 
no  telling  how  long  the  ammonia  has  stood  on  some  dealer's 
shelves.  The  still  may  be  kept  set  up  in  a  corner  of  the  hood 
and  the  operation  conducted  by  the  laboratory  boy.  By  using 
redistilled  ammonia  it  is  possible  to  do  away  with  the  second 
precipitation  of  the  iron  and  alumina,  which  is  made  necessary  by 
the  presence  of  ammonium  carbonate  in  the  ammonia  water,  as 
this  carbonate  precipitates  some  calcium  carbonate  along  with  the 
alumina. 

The  precipitate  of  iron  and  alumina  is  troublesome  to  wash, 
and  unless  it  is  freed  from  chlorides,  some  loss  of  iron,  by 
volatilization  as  ferric  chloride,  will  result  when  the  precipitate  is 
ignited.  In  order  to  avoid  this  tedious  washing,  the  writer  has 
always  followed  the  plan  of  dissolving  the  first  precipitate  in 
nitric  acid,  thus  avoiding  the  presence  of  chlorides  in  the  second 
precipitate  and  doing  way  with  the  tedious  washing.  When  this 
is  done  only  enough  washing  is  necessary  to  collect  the  precipi- 
tate in  the  point  of  the  filter.  This  plan  is  suggested  in  the  meth- 
od of  the  Lehigh  Valley  Committee. 

Calcium  oxalate  may  be  washed  with  hot  water.  Some  chemists 
prefer  to  add  a  little  ammonia  to  the  wash  water,  but  to  the 

t  Hildebrand,  >«r.  Amer.  Chem.  Sec.,  XXIV.,  369. 


l82  PORTLAND  CEMENT 

author  this  seems  unnecessary.  The  precipitate  should  always  be 
formed  in  a  boiling  ammoniacal  solution,  with  stirring,  and  al- 
lowed to  settle  before  filtering.  Some  chemists  heat  the  ammo- 
nium oxalate  solution  also  to  boiling  before  adding  to  the  boil- 
ing solution  containing  the  calcium.  Sufficient  ammonium  oxa- 
late should  always  be  added  to  convert  all  the  magnesium  present 
as  well  as  the  calcium  to  oxalate,  else  the  precipitation  of  the  cal- 
cium will  be  incomplete.  Nothing  is  gained  by  allowing  the  lime 
more  than  15  or  20  minutes  to  settle. 

Magnesium  oxalate  is  not  very  soluble  and  if  magnesia  is 
present  in  large  amount  will  be  precipitated  with  the  lime.  On 
the  other  hand,  calcium  oxalate  is  slightly  soluble  in  hot  water. 
As  cement  contains  such  a  small  percentage  of  magnesia  the 
quantity  carried  down  with  the  lime  is  usually  less  than  o.i  per 
cent.,  and  as  the  quantity  of  calcium  oxalate  which  goes  into  solu- 
tion is  precipitated  with  the  magnesia,  the  two  errors  tend  to 
balance  each  other.  The  factors  entering  into  a  clean  separa- 
tion of  lime  and  magnesia  are  that  there  must  be  an  excess  of 
ammonium  oxalate  and  that  the  solution  should  measure  at  least 
300  cc. 

Directions  for  making  the  solution  for  determining  lime  volu- 
metrically  and  for  carrying  out  the  process  will  be  found  on  page 
185.  The  volumetric  determination  is  very  accurate  and  under 
ordinary  technical  conditions,  when  many  analyses  are  made 
every  day,  will  prove  as  trustworthy  as  the  gravimetric.  When 
an  occasional  determination  only  is  made  the  latter  will  prove 
more  useful. 

Calcium  oxalate  on  ignition  over  a  burner  to  very  faint  redness 
changes  to  calcium  carbonate.  If  the  heating  is  increased  and 
the  blast  is  used  calcium  oxide  is  formed.  Instead  of  weighing 
as  the  oxide  some  chemists  prefer  to  weigh  as  a  sulphate.  To 
do  this,1  dry  the  precipitate  perfectly,  detach  it  as  far  as  possi- 
ble from  the  filter  to  a  piece  of  black  glazed  paper.  Burn  the 
filter-paper  in  a  weighed  platinum  crucible,  and  when  all  car- 
bonaceous matter  is  burned,  brush  the  precipitate  into  the  crucible 
from  the  glazed  paper.  Drop  concentrated  sulphuric  acid  on  the 
precipitate  till  it  is  well  moistened,  avoiding  an  excess,  and  heat 

1  I^ord,  "Notes  on  Metallurgical  Analysis,"  p.  n. 


ANALYTICAL  METHODS  183 

the  crucible  under  a  hood  cautiously,  from  a  burner  held  in  the 
hand,  until  the  swelling  of  the  mass  subsides  and  the  excess  of 
sulphuric  acid  has  been  driven  off,  as  shown  by  the  disappearance 
of  the  white  fumes  coming  from  the  crucible.  Then  heat  for  five 
minutes  to  a  cherry  red  heat,  but  do  not  use  the  blast.  Cool  and 
weigh  as  calcium  sulphate,  which  multiplied  by  0.41185  gives  the 
equivalent  of  lime,  CaO. 

Mr.  W.  H.  Hess  uses  the  following  method1  for  converting 
the  calcium  oxalate  to  calcium  sulphate.  After  burning  off  all  the 
carbon  of  the  filter-paper,  the  crucible  is  allowed  to  cool  partly, 
when  a  portion  of  chemically  pure  dry  ammonium  nitrate,  ap- 
proximately equal  in  bulk  to  the  lime  in  the  crucible,  and  about 
twice  as  much  chemically  pure  fused  ammonium  sulphate  are 
added.  A  tight-fitting  cover  is  now  placed  on  the  platinum  cru- 
cible and  then  gentle  heat  is  applied.  Mr.  Hess  found  it  very 
convenient  to  incline  the  crucible  at  an  angle  of  30°,  allowing 
the  tip  of  the  crucible  cover  to  project  outward,  and  then  apply 
the  flame  to  the  tip  of  the  cover,  gradually  bringing  the  flame 
under  the  crucible  as  the  reaction  grows  less  and  less  violent. 
The  reaction  is  complete  when  fumes  of  ammonia  salts  are  no 
longer  driven  off.  Intense  ignition  is  unnecessary  and  is  to  be 
avoided.  The  crucible  should  be  weighed  with  its  cover. 

The  evaporation  of  the  filtrate  from  the  lime  may  be  rapidly 
carried  out,  in  a  large  porcelain  dish,  in  the  following  manner: 
Place  a  piece  of  wire  gauze  on  a  tripod  and  in  the  centre  of  this, 
lay  a  disk  of  asbestos  paper,  the  size  of  a  silver  dollar.  Now  set 
the  dish  on  the  gauze  and  place  a  Bunsen  burner,  with  its  flame 
turned  low,  so  that  the  latter  comes  under  the  asbestos.  The 
solution  will  then  evaporate  rapidly,  and  yet  without  ebullition, 
or  loss  by  spurting. 

Magnesium  pyrophosphate  is  quite  soluble  in  hot  water,  less 
so  in  cold  water,  and  practically  insoluble  in  water  rendered 
strongly  ammoniacal.  It  should  be  washed,  therefore,  with  a 
mixture  of  water  and  ammonia.  Some  chemists  use  no  am- 
monium nitrate  in  their  washing  fluid,  and  mix  in  proportions 
varying  from  ten  to  three  parts  water  for  one  part  of  ammonia. 
It  is  a  difficult  precipitate  to  ignite  perfectly  white,  but  the  blast 

^•Jour.  Amer,  Chem.  Soc.,  22,  477. 


184  PORTLAND   CEMENT 

lamp  should  never  be  used  in  the  attempt  to  make  it  so,  as  de- 
struction of  the  platinum  crucible  might  follow.  The  precipitate 
may  be  ignited  wet  if  a  low  flame  is  used  at  first. 

A  Gooch  crucible  may  be  used  in  place  of  a  filter  paper,  al- 
though it  is  much  less  convenient.  It  consists  of  a  flat-bottomed, 
perforated  crucible  provided  with  a  cap  (Fig.  41).  The  perfora- 
ted crucible  is  placed  in  one  end  of  a  piece  of  soft  rubber  tubing 
of  large  bore,  the  other  end  of  which  is  stretched  over  a  small  fun- 
nel passing  into  a  flask  through  a  rubber  stopper  (Fig.  42).  The 


Fig.  41,  Gooch  Crucible.  Fig.  42,  Gooch  Crucible  in  Use. 

flask  is  connected  with  the  filter  pump.  To  prepare  the  filter, 
pour  a  little  prepared  asbestos  (purified  by  washing  with  hot 
concentrated  hydrochloric  acid)  suspended  in  water  into  the  cru- 
cible and  attach  the  suction  to  the  flask.  The  asbestos  at  once 
forms  a  thick  felt  over  the  bottom  of  the  crucible,  which  by  using 
the  suction  may  be  readily  washed  with  water.  After  washing, 
suck  dry  as  possible  with  the  pump,  remove  from  the  funnel,  de- 
tach any  pieces  of  asbestos  that  may  be  on  the  outside  of  the 
bottom  of  the  crucible,  cap,  ignite,  and  weigh.  Remove  the  cap, 
attach  to  the  funnel  as  before,  apply  the  suction  and  pour  the 
liquid  to  be  filtered  through  the  crucible,  wash,  cap,  dry,  if  nec- 
essary, ignite  and  weigh  as  before.  The  crucible  and  cap  may 
be  purchased  from  dealers  in  platinum  or  chemical  ware. 

The  use  of  platinum  dishes  is  recommended  for  the  solution 
and  evaporation  of  the  sample  because  platinum  is  a  much  better 
conductor  of  heat  than  porcelain  and  glass,  and  consequently 
evaporations  can  be  carried  out  much  more  rapidly  in  them  than 


ANALYTICAL  METHODS 


185 


in  anything  else.     There  is  also  no  danger  of  contaminating  the 
analysis  with  silica  from  the  dish. 

Crucibles  in  which  silica  has  been  ignited  may  be  most  conven- 
iently cleaned  by  boiling  in  them  a  little  hydrofluoric  acid.  Cru- 
cibles used  to  ignite  iron  and  alumina  are  best  cleansed  by  boil- 
ing in  them  dilute  (i-i)  hydrochloric  acid,  while  those  used  for 
barium  sulphate  can  be  cleaned  by  strong  sulphuric  acid  and 
warming.  Magnesium  pyrophosphate  may  be  readily  removed 
from  platinum  or  porcelain  crucibles  by  placing  the  latter  in  a 
beaker  of  ten  per  cent,  hydrochloric  acid  and  boiling.  The  dilute 
acid  in  this  case  will  do  the  work  when  strong  acid  will  fail.  No 
appreciable  loss  in  weight  of  the  crucible  will  be  occasioned  by 
any  of  the  above  treatments. 

VOLUMETRIC  DETERMINATION  OF  LIME. 

Preparation  of  the  Standard  Permanganate. 
Dissolve  the  quantity  of  pure  crystallized  potassium  permanga- 
nate shown  in  the  table  below,  in  the  desired  amount  of  water, 
using  a  balance  accurate  to  at  least  0.5  per  cent,  of  the  weight  of 
permanganate  to  be  taken,  and  measuring  the  water  with  a  grad- 
uated flask.  In  this  way,  a  solution  can  be  made  of  sufficiently 
near  the  correct  strength  for  the  use  of  the  table  in  the  appendix. 

TABLE  XX. — FOR  PREPARING  STANDARD    PERMANGANATE  OF  APPROXI- 
MATELY THE  STRENGTH  i  cc.  =  o  005  GRAM  CaO. 
5.64  grams  KMnO4  to     I  liter  of  water 
11.28       " 


16.92 
22.56 
28.20 

33-84 
39-48 
45-12 
50.76 
56.40 


10 


Use  a  balance  accurate  to  at  least  0.5  per  cent,  of  the  weight 
of  KMnO4  to  be  taken  and  measure  the  water  with  a  graduated 
flask. 

The  simplest  way  to  make  the  solution,  is  to  weigh  out  the 
permanganate  and  place  in  the  bottle  with  the  water,  some  week 


l86  PORTLAND  CEMENT 

or  ten  days  before  the  solution  is  to  be  standardized.  The  con- 
tents of  the  bottle,  which  is  kept  in  a  dark  place,  is  shaken  every 
now  and  then  for  the  first  two  or  three  days.  When  the  solution 
is  needed,  it  is  siphoned  off  into  another  bottle,  leaving  about  an 
inch  of  solution  in  the  old  bottle.  A  glass  siphon  is  used  and  its 
end  should  not  extend  nearer  than  an  inch  from  the  bottom  of 
the  bottle.  The  solution  in  the  new  bottle  is  now  shaken  and 
standardized.  The  writer  in  his  laboratory  used  eight  liter  (2 
gallon  bottles)  and  this  quantity  of  permanganate  will  last  him 
from  two  to  three  weeks.  The  solution  should  be  standardized 
every  week.  It  will  be  found  more  convenient  to  make  the  solu- 
tion as  above  and  standardize  every  week,  than  to  attempt  to 
make  a  solution  which  will  not  change,  by  boiling  and  filtering 
as  directed  by  Morse.1 

The  permanganate  solution  should  be  kept  in  a  dark  place. 
Fig.  43  shows  the  arrangement  for  storing  and  using  the  per- 
manganate adopted  by  the  writer.2 

Standardizing  the  Permanganate. 

To  standardize  the  permanganate,  weigh  into  a  400  cc.  beaker 
0.5  gram  of  powdered  calcite;  add  100  cc.  of  water  and  10  cc. 
of  hydrochloric  acid,  cover  with  a  watch  glass  and  boil  until  all 
carbon  dioxide  is  expelled.  When  completely  dissolved,  dilute 
to  the  usual  volume  in  which  the  lime  precipitation  is  made  in  an 
analysis,  and  make  alkaline  with  ammonia.  Add  20  cc.  of  a 
boiling  saturated  solution  of  ammonium  oxalate,  continue  boil- 
ing and  stirring  for  a  few  minutes,  let  settle,  filter  and  wash  thor- 
oughly with  hot  water  using  not  more  than  125  cc.  of  the  liquid. 
Transfer  the  filter  and  precipitate  to  the  beaker  in  which  the  pre- 
cipitation was  made,  spreading  the  paper  against  the  side  and 
washing  down  the  precipitate  first  with  hot  water  and  then  with 
dilute  sulphuric  acid  (1-4).  Remove  the  paper,  add  50  cc.  of 
water  and  10  cc.  concentrated  sulphuric  acid,  heat  to  incipient 
boiling  and  titrate  with  permanganate.  The  factor  for  lime, 
CaO,  is  found  by  dividing  0.56  by  the  number  of  cubic  centi- 
meters of  permanganate  taken  and  for  calcium  carbonate,  CaCO3, 
by  dividing  100  by  the  number. 

1  Amer.  Chem.Jour.,  XVIII.,  401. 

2  Chemical  Engineer,  I.,  288. 


ANALYTICAL  METHODS 


i87 


The  above  method  is  that  recommended  by  the  Committee  of 
the  Lehigh  Valley  Section  of  the  American  Chemical  Society  on 
the  Uniform  Analysis  of  Cement  and  Cement  Materials.  Some 
operators  prefer  to  use  ferrous  ammonium  sulphate  for  stand- 
ardizing. The  usual  method  of  using  this  is  as  follows : 


Fig.  43,  Table  for  Titrations. 

Weigh  into  each  of  two  beakers  1.4  grams  of  pure  crystallized 
ferrous  ammonium  sulphate,  add  cold  water,  allow  the  salt  to 
completely  dissolve  without  stirring  and  then  add  10  cc.  of 
dilute  sulphuric  acid.  Stir  and  run  in  the  permanganate  from  a 


1 88  PORTLAND  CEMENT 

burette  until  the  color  of  the  solution  in  the  beaker  just  changes 
to  pink.  The  weight  of  the  double  salt  used  divided  by  14,  and 
then  by  the  number  of  cubic  centimeters  of  permanganate  re- 
quired, will  give  the  lime,  CaO,  value  per  cubic  centimeter,  for 
the  permanganate.  The  duplicate  titrations  should  check  closely ; 
if  not,  another  pair  should  be  run.  For  other  methods  of  stand- 
ardizing the  permanganate  solution  see  "Determination  of  Ferric 
Oxide." 

Calcite  in  the  form  of  Iceland  Spar  can  be  obtained  of  great 
purity,  and  may  be  generally  taken  as  100  per  cent.  CaCO3.  In 
purchasing  a  new  lot  it  should  be  specified  that  the  purest  grade 
is  wanted  "for  standardizing."  On  receipt  it  should  be  pow- 
dered to  pass  a  loo-mesh  sieve  and  kept  in  a  glass-stoppered 
bottle.  From  this  a  small  portion  should  be  taken  and  placed  in 
an  ounce  wide  mouth  bottle,  provided  with  either  a  glass  or  rub- 
ber stopper.  This  small  sample  should  be  dried  at  from  100- 
110°  C.,  and  on  removal  from  the  drying  oven  kept  tightly  stop- 
pered. The  calcite  should  then  be  checked  by  a  careful  analysis 
for  silica,  iron  oxide  and  alumina  and  the  lime  determined  grav- 
imetrically  as  on  page  172.  A  blank  should  be  run  at  the  same 
time;  that  is,  a  dish  is  selected  and  acid  added  to  it  just  as  if  it 
contained  a  sample,  etc.  The  small  residues  found  after  each 
step  should  be  deducted  from  those  found  on  analysis  of  the  cal- 
cite. The  sample  used  in  the  writer's  laboratory  gave  less  than 
o.i  per  cent,  impurities  when  treated  in  this  manner  and  56.02 
per  cent,  lime,  so  for  practical  purposes  it  has  been  considered  as 
loo  per  cent.  pure.  The  small  sample  of  calcite  should  be  dried 
after  the  bottle  has  been  opened  for  five  or  six  determinations,  as 
it  will  take  up  some  moisture  from  the  air. 
The  Determination. 

Directions  for  determining  the  lime  volumetrically  are  given 
on  page  174. 

Notes. 

The  method  depends  upon  the  reaction  between  oxalic  acid  and 
potassium  permanganate. 

5H2C2O4  +  2KMnO4  +  sH2SO4  =  ioCO2  +  K,SO4  +  2MnSO4  +  8H2O 
The  reaction  between  iron  and  permanganate  is 
ioFeS04  +  2KMn04  +  8H2SO4  =  5Fe.2(SO4)3  -f  2MnSO4  +  K2SO4  +  8H2O. 


ANALYTICAL  METHODS  189 

Hence  5  molecules  H2CVO4  =  2  mols.  KMnO4  =  10  niols.  FeSO4  or  5 
tiiols.  H2C2O2  (=  5  mols.  CaO)  =  ro  mols.  FeSO±  (=  10  atoms  Fe). 

Then  5  mols.  CaO  =  10  atoms  Fe,  and  5(4^+  16)  CaO  =  10  X  56  Fe,  or 
280  CaO  ==  560  Fe. 

Hence,  CaO   :  Fe  : :  280  :  560,  from  which  CaO  =  Fe  or  — Fe. 

So  the  iron  value  of  any  permanganate  solution  divided  by  2 
will  give  its  lime  value. 

The  titration  with  permanganate  must  be  made  with  a  hot  so- 
lution between  60°  and  70°  C.  In  the  scheme  given,  the  solu- 
tion is  heated  by  the  action  with  the  strong  sulphuric  acid,  added 
just  before  titration. 

RAPID  DETERMINATION  OP  LIME  WITHOUT  SEPA- 
RATION OF  SILICA,  ETC.1 

Weigh  0.5  gram  of  cement  into  a  dry  500  cc.  beaker  and  add, 
with  constant  stirring,  20  cc.  of  cold  water.  Break  up  the  lumps 
and  when  all  the  sample  is  in  suspension,  except  the  heavier  par- 
ticles, add  20  cc.  of  dilute  (i-i)  hydrochloric  acid  and  heat  until 
.solution  is  complete.  This  usually  takes  5  or  6  minutes.  Heat 
to  boiling  and  add  dilute  ammonia  (0.96  sp.  gr.)  carefully  to  the 
solution  of  the  sample  until  a  slight  permanent  precipitate  forms. 
Heat  to  boiling  and  add  10  cc.  of  a  10  per  cent,  solution  of  oxalic 
acid.  Stir  until  the  oxides  of  iron  and  aluminum  are  entirely 
dissolved  and  only  a  slight  precipitate  of  calcium  oxalate  re- 
mains. Now  add  200  cc.  of  boiling  water  and  sufficient  (20  cc.) 
.saturated  solution  of  ammonium  oxalate  to  precipitate  the  lime. 
Boil  and  stir  for  a  few  moments,  remove  from  the  heat,  allow 
the  precipitate  to  settle  and  filter  on  an  n  cm.  filter.  Wash  the 
precipitate  and  paper  ten  times  with  hot  water  using  not  more 
than  10  or  15  cc.  of  water  each  time.  Remove  the  filter  from 
the  funnel,  open  and  lay  against  the  sides  of  the  beaker  in  which 
the  precipitation  was  made,  wash  from  the  paper  into  the  beaker 
with  hot  water,  add  dilute  sulphuric  acid,  fold  the  paper  over 
and  allow  to  remain  against  the  walls  of  the  beaker.  Heat  to 
£0°  C.  and  titrate  wtih  standard  permanganate  until  a  pink  color 
is  obtained,  now  drop  in  the  filter  paper,  stir  until  the  color  is 
discharged  and  finish  the  titration  carefully  drop  by  drop. 

1  Chemical  Engineer*  I  ,  21. 


19°  PORTLAND  CEMENT 

Notts. 

The  above  method  for  the  determination  of  lime  is  dependent 
on  the  fact  that  lime  can  be  completely  precipitated  as  oxalate 
in  solutions  containing  free  oxalic  acid,  while  iron,  alumina  and 
magnesia  are  not.  The  method  as  outlined  above  was  worked 
out  by  the  writer  some  years  ago  and  has  been  in  constant  use 
in  the  laboratories  of  several  large  cement  companies  since  that 
time,  giving  entire  satisfaction. 

The  oxalic  acid  method  is  much  more  accurate  than  the  one 
sometimes  used  of  precipitating  the  iron  and  alumina  by  am- 
monia and  then  without  filtration  throwing  down  the  lime  as 
oxalate  in  the  same  solution,  since  in  the  latter  method  some  of 
the  lime  is  thrown  down  as  carbonate  and  hence  not  found  by 
the  permanganate.  It  is  just  as  rapid  as  the  above  because  the 
only  extra  step  is  the  addition  of  10  cc.  of  oxalic  acid  solution 
which  is  more  than  made  up  for  by  the  more  rapid  filtration  due 
partly  to  the  fine  granular  precipitate  of  calcium  oxalate  ob- 
tained and  also  to  this  not  being  contaminated  by  the  flocculent 
alumina  precipitate. 

The  oxalic  acid  method  is  just  as  accurate  as  the  longer  one  of 
separating  the  silica,  iron,  and  alumina  from  the  solution,  before 
precipitating  the  lime.  Indeed  unless  the  iron  and  alumina  are 
separated  by  double  precipitation  it  is  the  more  accurate  of  the 
two. 

A  determination  can  be  made  by  the  above  method  in  from  25 
to  30  minutes,  of  which  10  or  15  are  required  for  the  lime  ta 
settle.  The  ammonia  must  not  be  added  in  very  large  excess 
and  to  guard  against  this  the  addition  can  best  be  made  from 
the  bottle  shown  in  Fig.  40,  on  page  180. 

DETERMINATION  OF  FERRIC  OXIDE. 
By  Titration  with  Potassium  Permanganate*      ( Marguerite's 

Method,) 

Standard  Potassium  Permanganate. 

Dissolve  i. 975 -grams  of  pure  crystallized  potassium  permanga- 
nate in  100  cc.  of  water,  boil  and  allow  to  stand  all  night.  In  the 
morning  filter  through  asbestos  into  a  bottle  and  dilute  to  I  liter. 
To  test,  or  standardize,  the  solution,  weigh  into  each  of  two  beak- 
ers 0.4900  gram  of  pure  ferrous  ammonium  sulphate,  equivalent 


ANALYTICAL  METHODS  IQI 

to  o.i  gram  of  ferric  oxide,  Fe2O3.  Dissolve  in  50  cc.  of  water, 
without  heating,  add  10  cc.  of  dilute  sulphuric  acid  and  run  in 
the  permanganate  from  a  burette  until  the  color  of  the  solution 
in  the  beaker  just  begins  to  turn  pinkish.  Take  the  reading  of  the 
burette  and  then  add  another  drop,  which  should  cause  the  solu- 
tion to  become  decidedly  pinkish.  Divide  the  weight  of  ferric 
oxide  (o.i  gram)  equivalent  to  the  weight  of  ferrous  ammonium 
sulphate  taken  for  the  titration  (0.49  gram)  by  the  number  of 
cubic  centimeters  of  permanganate  required;  the  result  will  give 
the  ferric  oxide  equivalent  to  I  cc.  of  the  permanganate. 

To  use  iron  wire  in  standardizing,  clean  two  pieces  of  fine  iron 
wire,  weighing  o.i  gram  each,  by  rubbing  first  between  emery 
paper  and  then  with  a  cloth.  Coil  around  a  lead  pencil  and  weigh 
each  coil.  Put  30  cc.  of  dilute  sulphuric  acid  in  a  strong  gas 
bottle  provided  with  a  perforated  stopper  through  which  passes 
a  perfect  fitting  glass  tube  with  a  hole  blown  in  its  side  (Fig. 
44).  Heat  the  acid  to  boiling  and  drop  in  a  coil  of  wire.  When 


Fig.  44,  Stopper  and  Valve  for  Iron  Reductions. 

the  solution  of  the  latter  is  complete,  remove  the  bottle  from  the 
.source  of  heat  and,  after  closing  the  opening  by  pushing  the  per- 
forated glass  tube  down  until  its  opening  is  closed  by  the  stopper, 
allow  the  gas  bottle  to  cool.  When  cold  titrate  the  solution  with 
the  permanganate  solution  as  above.  Multiply  the  weight  of 
the  iron  wire  by  0.003  an<^  deduct  the  result  from  the  original 
weight  for  impurities.  Multiply  the  corrected  weight  by  1.4286, 
or  divide  by  0.7,  and  divide  by  the  number  of  cubic  centimeters 
of  permanganate  required.  The  result  will  be  the  ferric  oxide 
equivalent  of  I  cc.  of  the  standard  potassium  permanganate.  Re- 
peat the  test  with  the  other  weighed  coil  of  iron  wire.  The 
values  for  each  cubic  centimeter  of  permanganate  by  the  two 
titrations  should  agree  closely.  Yet  another  way  is  to  dissolve 
the  iron  wire  in  15  cc.  of  dilute  sulphuric  acid  in  a  beaker,  cool, 


I92  PORTLAND  CEMENT 

dilute,  pass  through  the  reductor,  described  on  page   191,  and 
titrate  with  the  permanganate,  calculating  the  results  as  above. 
The  Determination. 

The  Committee  on  Uniformity  in  Analysis  of  Materials  for  the 
Portland  Cement  Industry,  of  the  New  York  Section  of  the  So- 
ciety of  Chemical  Industry,  recommend  that  the  determination 
of  ferric  iron  be  conducted  on  the  ignited  precipitate  of  ferric 
oxide  and  alumina,  after  weighing,  in  the  following  manner : 

The  combined  iron  and  aluminum  oxides  are  fused  in  a  plati- 
num crucible  at  a  very  low  temperature  with  about  3  to  4  grams- 
of  KHSO4,  or,  better,  NaHSO4,  the  melt  taken  up  \vith  so  much 
dilute  H2SO4  that  there  shall  be  no  less  than  5  grams  absolute 
acid  and  enough  water  to  effect  solution  on  heating.  The  solu- 
tion is  then  evaporated  and  eventually  heated  till  acid  fumes 
come  off  copiously.  After  cooling  and  redissolving  in  water  the 
small  amount  of  silica  is  filtered  out,  weighed,  and  corrected  by 
HF1  and  H^SO/.  The  filtrate  is  reduced  by  zinc,  or  preferably 
by  hydrogen  sulphide,  boiling  out  the  excess  of  the  latter  after- 
wards whilst  passing  CO2  through  the  flask,  and  titrated  with 
permanganate.2  The  strength  of  the  permanganate  solution 
should  not  be  greater  than  .0040  gr.  Fe.,O3  per  cc. 

The  Committee  appointed  by  the  Lehigh  Valley  Section  of  the 
American  Chemical  Society  direct  also  that  the  determination. 
shall  be  carried  out  on  the  precipitate  of  oxide  of  iron  and  alum- 
ina. Their  method  differs  from  the  above  chiefly  in  the  manner 
of  reduction,  and  is  as  follows : 

Add  four  grams  acid  potassium  sulphate  to  the  crucible  con- 
taining the  ignited  oxides  of  iron  and  alumina,  and  fuse  at  a  very 
low  heat  until  oxides  are  wholly  dissolved — twenty  minutes  at 
least ;  cool ;  place  crucible  and  cover  in  small  beaker  with  50  cc. 
water;  add  15  cc.  dilute  sulphuric  acid  (1-4)  ;  cover  and  digest 
at  nearly  boiling  until  melt  is  dissolved ;  remove  crucible  and 
cover,  rinsing  them  carefully.  Cool  the  solution  and  add  10 

1  This  correction  of  A^Os  Fe2O3  for  silica  should  not  be  made  when  the  HF1  correc- 
tion of  the  main  silica  has  been  omitted,  unless  that  silica  was  obtained  by  only  one  evap- 
oration and  nitration.     After  two  evaporations  and  nitrations  i  to  2  mg.  of  SiO2  are  still 
to  be  found  with  the  A1£O3  Fe2O3. 

2  In  this  way  only  is  the  influence  of  titanium  to  be  avoided  and  a  correct  resxilt  ob- 
tained from  iron. 


ANALYTICAL  METHODS  193 

grams  powdered  C.  P.  zinc,  No.  20.  Let  stand  one  hour,  decant 
the  liquid  into  a  larger  beaker,  washing  the  zinc  twice  by  de- 
cantation,  and  titrate  at  once  with  permanganate.  Calculate  the 
Fe2O3  and  determine  the  A12O3  by  difference.  Test  Zn,  etc.,  by 
a  blank  and  deduct. 

Notes. 

Ferrous  salts  are  oxidized  by  potassium  permanganate  in  solu- 
tions containing  free  acid  to  ferric  salts  according  to  the  re- 
action, 

ioFeSO4  4-  2KMnO4  +  8H,SO4  =  5Fe2(SO4)3  -f  K2SO4  +  2MnSO4  +  8H2O. 
Potassium  permanganate  does  not  give  trustworthy  results  in  the 
presence  of  free  hydrochloric  acid. 

If  -the  permanganate  is  prepared  as  directed  above  it  is  not 
changed  very  rapidly,  provided  it  is  kept  in  a  dark  place.  It  is 
well  to  standardize  it  occasionally,  however. 

To  reduce  the  iron  with  hydrogen  sulphide,  place  the  solution 
into  a  flask  and  add  to  the  solution  one-tenth  its  volume  of  sul- 
phuric acid  and  25  cc.  of  strong  hydrogen  sulphide  water.  Heat 
to  boiling.  Now  stopper  the  flask  with  a  rubber  stopper  having 
two  perforations  through  which  two  tubes  pass.  One  tube  should 
reach  nearly  to  the  bottom  of  the  flask  and  the  other  just  inside 
the  stopper.  Boil  the  solution  until  all  hydrogen  sulphide  is  ex- 
pelled, passing  carbon  dioxide  through  the  flask  all  the  while, 
bringing  it  in  through  the  long  tube  and  out  through  the  short 
one.  The  expulsion  of  the  hydrogen  sulphide  may  be  tested  by 
holding  a  piece  of  filter  paper,  moistened  with  lead  acetate  or 
nitrate  solution,  in  the  escaping  steam  from  the  short  tube.  As 
long  as  any  hydrogen  sulphide  is  present  the  paper  is  blackened 
or  browned.  The  solution  must  be  cooled  in  a  current  of  carbon 
dioxide  before  titration  with  permanganate. 

In  dissolving  the  oxides  of  iron  and  aluminum  in  potassium  bi- 
sulphate,  the  operation  should  be  conducted  at  a  low  temperature, 
so  as  not  to  drive  off  the  excess  acid  in  the  salt.  The  contents 
of  the  crucible  should  therefore  be  just  hot  enough  to  keep  them 
fluid.  The  fusion  with  bisulphate  is  tedious,  however,  and  until 
recently  the  writer  determined  ferric  oxide  in  cement  by  the  fol- 
lowing methods.  It  is  simpler  than  the  above  schemes  and  has 

7 


194  PORTLAND  CEMENT 

the  advantage  of  allowing  a  sample  of  one  or  two  grams  to  be 
used  for  the  determinations : 

Weigh  i  gram  of  finely  ground  cement  into  a  beaker  and  add 
15  cc.  of  hydrochloric  acid.  Heat  for  ten  to  fifteen  minutes,  add 
200  cc.  of  water  and  heat  to  boiling.  Add  ammonia  in  slight  but 
distinct  excess,  boil  a  few  minutes,  allow  the  precipitate  to  settle, 
filter,  using  the  filter  pump  if  one  is  at  hand,  and  wash  two  or 
three  times  with  hot  water.  Place  a  clean  flask  under  the  funnel 
and  redissolve  the  precipitate  in  a  mixture  of  15  cc.  dilute  sul- 
phuric acid  and  60  cc.  water,  made  up  in  the  beaker  in  which  the 
precipitation  was  effected.  Wash  the  filter  and  silica  free  from 
iron  with  cold  water,  pass  through  the  reductor,  described  below, 
and  titrate  the  solution  with  permanganate.  Multiply  the  number 
of  cubic  centimeters  of  standard  permanganate  required  by  the 
ferric  oxide  value  of  the  permanganate  and  then  by  100.  Divide 
the  result  by  the  weight  of  cement  taken ;  the  quotient  will  be  the 
per  cent,  of  ferric  oxide,  Fe2O3,  in  the  cement. 

The  form  of  reductor  best  suited  to  cement  work  is  the  design 
of  Dr.  Porter  W.  Shinier,  of  Easton,  Pa.  His  description  of  the 
apparatus1  is  as  follows:  "The  reductor  tube  (Fig.  45)  is  a 
plain  glass  tube,  three-eighths  inch  internal  diameter,  drawn  out 
and  cut  off  at  its  lower  end.  It  is  filled  by  placing  a  few  small 
pieces  of  broken  glass  in  the  drawn-out  portion,  and  on  this 
about  an  inch  of  well  cleaned  sand.  The  tube  is  then  filled  with 
amalgamated  zinc  of  as  nearly  uniform  twenty  mesh  size  as  pos- 
sible. About  80  grams  are  required.  No  asbestos  or  glass  wool 
is  used.  The  sand  prevents  particles  of  zinc  from  falling  through 
and  it  does  not  become  clogged  by  use.  The  consumption  of  zinc 
is  very  small,  and  when  the  column  has  settled  about  an  inch  a 
little  fresh  zinc  can  easily  be  poured  in  from  above.  The  re- 
ductor tube  is  united  with  a  4-inch  funnel  by  means  of  rubber 
tubing,  well  tightened  with  wire.  Between  the  funnel  and  re- 
ductor is  a  Hoffman  clamp.  The  lower  end  of  the  tube  passes 
through  a  soft  two-hole  stopper  so  far  as  to  reach  half  way  to 
the  bottom  of  a  heavy-walled  pint  gas-bottle.  The  gas-bottle  is 
connected  with  a  filter  pump  through  an  intermediate  safety  bottle 
and  valve.  The  funnel  is  clamped  to  a  retort  stand  in  such  a 

1  Jour.  Amer.  Chem.  Soc.,  XXI,  723. 


ANALYTICAL  METHODS 


195 


manner  as  to  allow  the  tube  and  gas  bottle  to  swing  easily  in  all 
directions.  It  is  well  to  adjust  the  height  so  as  to  leave  the  gas 
bottle  raised  slightly  above  the  base.  The  passage  'of  the  solu- 
tion through  the  reductor  may  be  effected  either  by  use  of  the 
pump  or  by  means  of  a  vacuum  obtained  by  condensation  of 
steam,  devised  originally  in  Bunsen's  laboratory.  In  using  the 
latter  method  a  little  water  may  be  boiled  in  the  gas  bottle  until 
all  air  is  expelled,  and  then  quickly  unite  with  the  reductor,  the 
clamp  on  the  filter  pump  being  closed.  The  speed  of  filtration  is 


Fig.  45,  Shimer's  Reductor. 

regulated  by  the  upper  clamp.  Instead  of  filling  the  gas  bottle 
with  steam  by  boiling  water  in  it,  it  is  better  to  have  a  conven- 
ient tin  or  copper  can  containing  boiling  water  and  provided 
with  one  or  more  short  steam  outlet  tubes  on  top.  The  empty 
gas  bottle  is  inverted  over  one  of  these  steam  outlets  and,  when 
filled  with  live  steam,  is  taken  off  and  united  as  quickly  as  possi- 
ble with  the  reductor.  This  latter  method  has  the  advantage  of 
starting  with  an  empty  gas  bottle  which  is  desirable  on  the  score 
of  accuracy." 

To  use  the  reductor  first  pass,  by  the  aid  of  suction,  about  50 


196  PORTLAND   CEMENT 

cc.  of  cold  dilute  sulphuric  acid  (i  part  acid  to  20  parts  of  \vater) 
through  the  reductor,  and  then  follow  with  200  cc.  of  cold  dis- 
tilled water.'  The  Hoffman  clamp  should  be  closed  before  all 
the  water  has  run  out  of  the  funnel  so  as  to  keep  the  tube  full 
of  water.  Now  empty  the  flask,  again  attach  to  the  tube,  pour 
the  iron  solution  into  the  funnel  and  open  the  clamp.  Just  be- 
fore the  funnel  becomes  empty,  run  water  around  its  sides  and 
rinse  the  beaker  well  witri  \vater,  running  the  washings  also 
through  the  reductor,  using  about  100  to  150  cc.  of  water  to  wash 
the  funnel  and  beaker.  The  time  required  for  the  iron  solution 
to  filter  through  the  zinc,  should  be  regulated  by  the  upper  clamp 
to  occupy  from  three  and  a  half  to  five  minutes. 

Instead  of  reducing  the  iron  solution  by  means  of  a  reductor, 
the  gas  bottle,  mentioned  on  page  191,  may  be  used.  Pour  the 
solution  into  the  bottle.  Add  I  gram  of  granulated  zinc,  stopper 
and  allow  to  stand  until  the  evolution  of  hydrogen  slackens ;  then 
heat  to  boiling.  When  the  zinc  is  completely  dissolved  (it  may 
be  necessary  to  add  more  acid  to  effect  this),  push  down  the  glass 
tube,  cool,  and  after  adding  10  cc.  of  dilute  sulphuric  acid  titrate 
with  the  permanganate. 

The  reduction  may  be  accomplished  with  hydrogen  sulphide 
also.  The  idea  of  the  use  of  hydrogen  sulphide  is  to  do  away 
with  the  error  introduced  by  the  presence  of  a  small  percentage 
of  titanium,  always  found  in  cement.  Titanium  is  reduced  by 
zinc,  and  then  oxidized  by  permanganate,  causing  the  results  for 
iron  to  be  high.  It  is  not  reduced  by  hydrogen  sulphide,  hence 
the  use  of  the  latter.  If  the  titanium  is  not  determined  and  de- 
ducted from  the  alumina,  however,  the  latter  is  too  high,  by  just 
so  much  so  that  for  practical  purposes  we  might  as  well  call 
titanium  iron  and  use  zinc  as  a  reducing  agent,  as  call  it  alumi- 
num and  use  hydrogen  sulphide. 

By  Titration  with  Potassium  Bichromate.     (Penny's  Method). 

Standard  Potassium  Bichromate. 

Place  from  10  to  15  grams  of  C.  P.  potassium  bichromate  in  a 
sufficiently  large  platinum  crucible.  Heat  carefully,  avoiding  all 
contact  of  the  flame  with  the  contents  of  the  crucible,  until  the 
salt  just  fuses  to  a  dark  liquid.  Then  withdraw  at  once  from 


ANALYTICAL  METHODS  197 

the  flame  and  let  the  crucible  cool.  Weigh  3.074  grams  of  the 
fused  bichromate,  which  in  cooling  will  have  crumbled  to  a  pow- 
der, dissolve  in  250  to  300  cc.  of  cold  water  and  pour  into  a 
liter  graduated  flask.  Rinse  out  the  beaker  several  times  into 
the  flask  and  dilute  the  solution  to  the  liter  mark.  Mix  well. 
One  cc.  of  this  solution  should  be  equivalent  to  0.005  gram  of 
ferric  oxide,  Fe2O3. 

To  test  or  standardize  the  solution,  weigh  into  a  small  beaker 
0.4900  gram  of  pure  ferrous  ammonium  sulphate  (equivalent  to 
o.i  gram  of  ferric  oxide).  Dissolve  in  50  cc.  of  water  and,  when 
all  the  salt  is  in  solution,  add  5  cc.  of  dilute  hydrochloric  acid. 
Run  the  bichromate  solution  from  a  burette  into  the  liquid  in  the 
beaker  until  a  drop  of  the  iron  solution  placed  upon  a  white 
porcelain  plate,  and  mixed  by  stirring  with  a  drop  of  a  freshly 
made  i  per  cent,  solution  of  potassium  ferricyanide  no  longer 
assumes  a  blue  color,  but  instead  gives  a  yellow.  This  should 
require  20  cc.  of  the  bichromate  solution.  If  more  or  less,  re- 
peat the  test,  and  if  the  first  and  second  results  agree,  divide  o.i, 
the  ferric  oxide  equivalent  of  the  weight  of  the  ferrous  ammon- 
ium sulphate  used,  by  the  number  of  cubic  centimeters  of  bi- 
chromate required.  The  result  will  give  the  ferric  oxide  equiva- 
lent, or  value,  in  grams  for  each  cubic  centimeter  of  the  stand- 
ard potassium  bichromate. 

Some  operators  prefer  to  standardize  their  bichromate  against 
iron  wire.  In  this  case  clean  o.i  gram  of  fine  iron  wire  by  rub- 
bing between  fine  emery  paper  and  then  between  filter-paper. 
Coil  around  a  lead  pencil  and  weigh.  Drop  the  coil  in  a  small 
beaker,  add  20  cc.  of  dilute  hydrochloric  acid  and  heat  until  all 
the  wire  dissolves.  Wash  down  the  sides  of  the  beaker  with  a 
wash-bottle,  bring  the  contents  to  a  boil  and  drop  in  the  stan- 
nous  chloride  solution,  described  below,  slowly  until  the  last  drop 
turns  the  solution  colorless.  Remove  from  the  source  of  heat  and 
cool  the  liquid  rapidly  by  setting  the  dish  in  a  vessel  of  cold  water. 
When  nearly  cold  add  at  once  15  cc.  of  saturated  mercuric  chlor- 
ide solution,  and  stir  well.  Allow  to  stand  a  few  minutes  and 
titrate  with  the  bichromate  as  described  above.  Multiply  the 
weight  of  the  iron  wire  by  0.003  and  deduct  this  from  the  origi- 
nal weight,  for  the  impurities  in  the  wire.  The  corrected  weight 


198  PORTLAND   CEMENT 

divided  by  0.7  and  then  by  the  number  of  cubic  centimeters  of  bi- 
chromate required,  gives  the  ferric  oxide  equivalent  in  grams  to 
each  cubic  centimeter  of  the  standard  bichromate.  This  value 
should  be  checked  unless  within  the  limits  of  allowable  error  to 
0.005  gram. 

Stannous  Chloride  Solution. 

Dissolve  100  grams  of  stannous  chloride  in  a  mixture  of  300 
cc.  of  water  and  100  cc.  of  hydrochloric  acid.  Add  scraps  of 
metallic  tin  and  boil  until  the  solution  is  clear  and  colorless. 
Keep  this  solution  in  a  closely  stoppered  bottle  (best  a  dropping 
bottle)  containing  metallic  tin.  This  solution  should  be  kept  from 
the  air. 

Mercuric  Chloride  Solution. 

Make  a  saturated  solution  of  mercuric  chloride  by  putting  an 
excess  of  the  salt  in  a  bottle  and  filling  up  with  water  and  shak- 
ing as  the  solution  gets  low. 

The  Determination. 

Weigh  i  gram  of  finely  ground  cement  into  a  small  beaker  and 
add  15  cc.  of  dilute  hydrochloric  acid,  heat  from  ten  to  fifteen 
minutes  and  add  a  little  water.  Heat  to  boiling  and  filter  through 
a  small  filter,  washing  the  residue  well  with  water  and  catching 
the  filtrate  and  washings  in  a  porcelain  dish.  Add  to  the  solu- 
tion 5  cc.  of  dilute  hydrochloric  acid  and  bring  to  a  boil.  Add 
carefully,  drop  by  drop,  the  stannous  chloride  solution  until  the 
last  drop  makes  the  solution  colorless.  Remove  from  the  burner 
and  cool  the  liquid  by  setting  in  a  vessel  of  cold  water.  When 
nearly  cold  add  15  cc.  of  the  mercuric  chloride  solution  and  stir 
the  liquid  in  the  dish  with  a  glass  rod.  Allow  the  mixture  to 
stand  for  a  few  minutes,  during  which  time  a  slight  white  pre- 
cipitate should  form.  Run  in  the  standard  bichromate  solution 
carefully  from  a  burette  until  a  drop  of  the  iron  solution  tested 
with  a  drop  of  I  per  cent,  solution  of  potassium  ferricyanide  no 
longer  shows  a  blue,  but  instead  a  yellow  color.  Multiply  the 
number  of  cubic  centimeters  of  bichromate  used  by  the  ferric 
oxide  equivalent  per  cubic  centimeter  of  the  bichromate  and 
divide  the  product  by  the  weight  of  the  sample.  The  result  mul- 


ANALYTICAL  METHODS  199 

tiplied  by  100  gives  the  per  cent,  of  the  ferric  oxide,  Fe2O3,  in 
the  cement. 

Notes. 

Treatment  with  hydrochloric  acid  is  sufficient  to  dissolve  all 
except  a  mere  trace  of  iron  in  Portland  cement. 

A  strongly  acid  solution  of  ferric  chloride,  if  boiling  hot,  is 
instantly  reduced  to  ferrous  chloride  by  a  solution  of  stannous 
chloride  according  to  the  following  reaction: 

Fe2Clc  +  SnCl2  =  SnCl4  +  2FeCl2 

The  operator  can  tell  when  complete  reduction  has  taken  place 
by  the  disappearance  of  the  yellow  color  of  the  solution.  The 
excess  of  stannous  chloride  is  removed  by  addition  of  mercuric 
chloride  when  the  following  takes  place: 

SnCl2  +  2HgCl2  =  SnCl4  +  Hg2Cl2. 

The  precipitate,  Hg2Cl2  should  be  white;  if  colored  gray  too 
much  stannous  chloride  was  used  in  reduction  and  mercury  has 
been  formed.  As  mercury  reacts  with  the  bichromate,  when  the 
precipitate  formed  on  adding  mercuric  chloride  is  not  perfectly 
white,  but  is  colored  gray,  the  determination  should  be  repeated 
using  more  care  to  avoid  a  large  excess  of  the  tin  solution.  If  no 
precipitate  is  formed  on  addition  of  mercuric  chloride  the  stan- 
nous chloride  has  not  been  added  in  excess,  and  all  the  iron  will 
not  have  been  reduced  to  the  ferrous  state. 

Ferrous  salts  are  oxidized  to  ferric  compounds  by  bichromate 
when  in  a  solution  containing  a  considerable  excess  of  hydro- 
chloric or  sulphuric  acid.  The  reaction  is : 

6FeCl2+K2Cr207+i4HCl=3Fe2Cl6+Cr2Cl6+2KCl+7H20. 

The  ferrous  ammonium  sulphate  has  the  formula  Fe(NH4)2 
(SO4)2.6H2O.  It,  therefore,  contains  one-seventh  its  weight  of 
iron  and  is  equivalent  to  0.20408  of  its  weight  of  ferric  oxide, 
Fe203.  Fe203. 

To  make  a  I  per  cent,  solution  of  potassium  ferricyanide  dis- 
solve i  gram  of  the  salt  in  100  cc.  of  water.  Ferric  compounds 
give  a  yellow  color  to  this  solution,  while  ferrous  compounds  im- 
part an  intense  blue  color.  This  solution  must  always  be  made 
up  fresh  as  it  is  reduced  by  exposure  to  light. 


2OO  PORTLAND  CEMENT 

The  writer  has  experimented  considerably  with  the  above  meth- 
od during  the  past  year,  and  he  has  found  it  thoroughly  reliable. 
The  presence  of  titanium  does  not  affect  its  accuracy  and  a  deter- 
mination can  easily  be  made  in  from  15  to  20  minutes. 

DETERMINATION  OF  SULPHURIC  ACID. 
Gravimetric  Method. 

Weigh  one  gram  of  the  sample  into  a  small  dry  beaker  and 
stir  it  up  with  10  cc.  of  cold  water  until  all  lumps  are  broken  up 
and  the  lighter  particles  are  in  suspension.  Add  15  cc.  of  dilute 
(i-i)  hydrochloric  acid  and  heat  until  solution  is  complete.  Fil- 
ter through  a  small  paper  and  wash  the  residue  thoroughly.  Di- 
lute the  filtrate  to  250  cc.,  heat  to  boiling,  and  add  10  cc.  of  boil- 
ing 10  per  cent,  barium  chloride  solution.  Stir  well  and  allow  to 
stand  over  night.  Filter,1  ignite,  and  weigh  as  BaSO,4  which 
multiplied  by  0.34291  gives  SO3,  or  by  0.58565,  gives  calcium 
sulphate,  CaSO4.  In  this  latter  case  multiply  the  percentage  of 
calcium  sulphate  by  0.41185  and  deduct  from  the  percentage  of 
lime  for  the  true  percentage  of  calcium  oxide,  CaO. 

Photometric  Method. 

Jackson1  has  devised  a  rapid  photometric  method  for  deter- 
mining sulphuric  acid  which  is  very  convenient  for  checking  this 
constituent  in  a  large  number  of  samples. 

The  apparatus2  used  in  this  method  is  shown  in  Fig.  46. 
Above  is  a  glass  tube  closed  at  the  bottom  and  graduated  in  milli- 
meters depth.  A  convenient  form  of  tube  is  a  Nessler  jar  2.5 
cm.  in  diameter  and  17  cm.  to  the  100  cc.  mark.  The  brass  holder 
for  this  tube  is  open  at  the  bottom  so  that  the  glass  tube  rests 
on  a  narrow  ring  at  this  point.  The  candle  below  is  so  adjusted 
by  means  of  a  spring  that  the  top  edge  is  always  just  three  inches 
below  the  bottom  of  the  glass  tube.  The  illustration  shows  the 
candle  with  the  regulator  cap  removed  so  as  to  better  represent 
the  process.  The  English  Standard  Candle  is  preferred,  but  a 
common  candle  of  the  same  size  may  be  used.  This  candle  must 
always  be  properly  trimmed  and  the  determination  must  be  made 
rapidly  so  as  not  to  heat  the  liquid  to  any  extent.  The  most  ac- 

1  See  Note,  p.  206. 

2  Made  by  Baker  &  Fox,  83  Schermerhom  St.,  Brooklyn,  N,  Y. 
l  Chemical  Engineer,  I.,  6,  361. 


ANALYTICAL   METHODS 


2O I 


curate  work  is  obtained  in  the  dark  room,  and  the  candle  should 
be  so  placed  as  not  to  be  subjected  to  a  draft  of  air.  Care  should 
be  taken  to  keep  the  bottom  of  the  tube  clean  both  inside  and  out 
so  as  not  to  cut  out  any  of  the  light. 


Fig.  46,  Jackson's  Apparatus  for  the  Photometric  Determination  of  Sulphates. 

To  determine  the  sulphate  in  a  cement  weigh  out  one  gram, 
correct  to  centigrams,  and  rub  up  thoroughly  with  a  glass  rod  in 


2O2 


PORTLAND  CEMENT 


a  small  porcelain  dish,  or  casserole,  with  two  cubic  centimeters  of 
strong  hydrochloric  acid.  Add  about  ten  cubic  centimeters  of 
water  and  heat  to  boiling.  Filter  and  wash  with  a  small  amount 
of  hot  water  into  a  100  cc.  graduated  Nessler  jar,  and  fill  with 
cold  water  nearly  to  the  100  cc.  mark.  If  necessary  suction  may 
be  employed  in  filtering,  but  usually  a  folded  rib  filter  will  do. 
Now  add  two  grams  of  solid  barium  chloride  crystals  and  make 
up  to  the  100  cc.  mark  with  cold  distilled  water.  Pour  back  and 
forth  from  the  tube  to  a  beaker  until  all  of  the  barium  chloride  is 
dissolved.  The  solution  is  now  ready  for  examination. 
TABLE  XXI.— FOR  THE  DETERMINATION  OF  SULPHATE  IN  CEMENT. 


Depth 
cm. 

Per  cent. 
SO,. 

Depth 
Cm. 

Per  cent. 
S03. 

Depth 
Cm. 

Per  cent. 
S03. 

Depth 
Cm. 

Per  cent. 
S03. 

.O 

5-2 

4.0 

•4 

7.0 

0.8 

10.  0 

0.6 

.1 

4.8 

4-1 

•  4 

7-1 

0.8 

10.2 

0.6 

.2 

4.4 

4-2 

•  3 

7-2 

0.8 

IO.4 

0.6 

•3 

4-1 

4-3 

•  3 

7-3 

0.8 

IO.6 

0.5 

•4 

3-8 

4-4 

•  3 

7-4 

0.8 

10.8 

0.5 

•  5 

3-6 

4-5 

•3 

7.5 

0.8 

I  I.O 

0.5 

.6 

3-4 

4-6 

2 

7-6 

0.8 

1  1.2 

0.5 

•  7 

3-2 

4-7 

.2 

7-7 

0.7 

ii.  4 

0.5 

.8 

3-° 

4.8 

.2 

7-8 

0.7 

ii.  6 

0.5 

9 

2-9 

4.9 

.2 

7-9 

0.7 

1  1.  8 

0.5 

2.0 

2-7 

5-o 

.1 

8.0 

0.7 

12.0 

0.5 

2.1 

2.6 

5-1 

.1 

8.1 

0.7 

12.2 

0.5 

2.2 

2.5 

5-2 

.  I 

8.2 

0.7 

12.4 

0.5 

2-3 

2.4 

5-3 

.1 

8-3 

0.7 

12.6 

0.5 

2.4 

2-3 

5-4 

.0 

8.4 

0.7 

12.8 

0.4 

2-5 

2.2 

5-5 

.0 

8.5 

0.7 

13.0 

0.4 

2.6 

2.1 

56 

.O 

8.6 

0.7 

13-5 

0.4 

2.7 

2.  I 

5-7 

.O 

8-7 

0.7 

14.0 

0.4 

2.8 

2.O 

5-8 

.O 

8.8 

0.6 

M-5 

0.4 

2.9 

•9 

5-9 

.O 

8.9 

0.6 

15-0 

0.4 

3-0 

•9 

6.0 

0.9 

9.0 

o  6 

15-5 

0.4 

3-1 

.8 

6.1 

0.9 

9-[ 

0.6 

16.0 

0.4 

3-2 

•7 

6.2 

0.9 

9.2 

0.6 

16.5 

0.4 

3-3 

•  7 

6-3 

0.9 

9-3 

06 

17.0 

o-3 

34 

.6 

6-4 

0.9 

9-4 

0.6 

17-5 

o-3 

3-5 

6 

6-5 

0.9 

9-5 

0.6 

180 

°-3 

3-6 

.6 

6.6 

0.9 

9-6 

c,6 

I8.5 

0-3 

3-7 

•  5 

6.7 

0.8 

9-7 

0.6 

19.0 

0.3 

3-8 

•5 

68 

0.8 

98 

0.6 

19-5 

0.3 

3-9 

1.4 

6-9 

0.8 

99 

0.6 

2O.O 

o-3 

The  candle  is  trimmed  and  lighted ;  the  solution  is  poured  back 
and  forth  to  get  a  thorough  mixture  of  the  precipitate  of  barium 
sulphate;  and  the  glass  tube  is  placed  in  position  in  the  holder. 


ANALYTICAL  METHODS  203 

The  liquid  containing  the  precipitate  is  now  poured  into  the  grad- 
uated tube  until  the  sight  of  the  image  of  the  flame  of  the  candle 
is  just  visible.  Then  pour  in  a  few  drops  at  a  time  until  it  just 
disappears  from  view.  The  height  to  which  this  solution  stands 
in  the  tube  (reading  the  bottom  of  the  meniscus)  is  then  taken 
and  from  this  reading  the  percentage  of  sulphates  present  in  the 
cement  may  be  read  directly  from  the  following  table : 

DETERMINATION  OF  TOTAL  SULPHUR. 
By  Solution  in  HC1  and  Br. 

Weigh  one  gram  of  the  sample  into  a  dry  beaker  and  stir  it  up 
with  10  cc.  of  bromine  water  until  all  lumps  are  broken  up  and 
all  except  the  heavier  particles  are  in  suspension.  Add  15  cc.  of 
dilute  hydrochloric  acid  (i-i)  and  heat  until  solution  is  complete. 
Filter  oft  the  residue  through  a  small  filter  and  wash  thoroughly 
with  hot  water.  Dilute  to  250  cc.  and  boil  until  all  bromine  is 
expelled.  Now  to  the  boiling  solution  add  TO  cc.  of  10  per  cent, 
barium  chloride  solution,  also  boiling,  and  proceed  as  in  the  de- 
termination of  sulphates. 

By  Fusion  With  Na2CO3  and  KNO3. 

Place  i  gram  of  cement,  finely  ground  and  dried,  in  a  large 
platinum  crucible  and  thoroughly  mix  it  by  stirring  with  6  grams 
of  sodium  carbonate  and  a  little  sodium  or  potassium  nitrate. 

Fuse  the  mixture,  being  careful  to  avoid  contamination  from 
sulphur  in  the  gases  from  source  of  heat.  This  may  be  done  by 
fitting  the  crucible  in  a  hole  in  an  asbestos  board.  The  heating  of 
the  crucible  should  be  gradually  done  first  over  a  Bunsen  burner 
for  a  while  and  then  over  a  blast  lamp,  until  the  contents  of  the 
crucible  are  in  quiet  fusion.  Run  the  fused  mass  well  up  on  the 
sides  of  the  crucible  and  chill  by  dipping  the  bottom  of  the  cru- 
cible in  a  vessel  of  cold  water.  If  loose,  remove  the  mass  from 
the  crucible  to  a  beaker  and  cover  with  hot  water.  If  not  loose, 
fill  the  crucible  with  hot  water  and  digest  until  the  mass  breaks 
up ;  then  remove  to  the  beaker.  Cover  the  latter  with  a  watch 
glass  and  acidify  with  hydrochloric  acid.  When  effervescence 
ceases  remove  the  watch  glass,  rinse  into  the  dish  and  filter.  Di- 
lute the  filtrate  to  250  cc.  and  heat  to  boiling.  Add  10  cc.  of  10 
per  cent,  barium  chloride  solution,  also  heated  to  boiling.  Stir 


2O4  PORTLAND   CEMENT 

and  heat  for  a  few  minutes  and  proceed  as  in  the  determination 
of  sulphates. 

DETERMINATION  OF  SULPHUR  PRESENT  AS 
CALCIUM  SULPHIDE. 

Weigh  5  grams  of  cement  into  a  porcelain  dish,  and  triturate 
with  water  until  it  shows  no  further  tendency  to  set.  Then  wash 
out  into  the  flask  (Fig.  47)  and  cork  tightly.  Two-thirds  fill  the 


Fig.  47,  Apparatus  for  Determining  Sulphides. 

ten-inch  test  tube  with  a  solution  of  lead  oxide  in  caustic  potash 
made  by  adding  lead  nitrate  solution  to  potassium  hydroxide  so- 
lution (sp.  gr.  1.27)  until  a  permanent  precipitate  forms,  and  then 
filtering  off  the  solution  through  asbestos  after  allowing  the  pre- 
cipitate to  settle.  Run  into  the  flask  by  means  of  the  funnel  50 
cc.  of  dilute  hydrochloric  acid  and  apply  heat  gently.  Finally 
bring  the  acid  to  a  boil  and  disconnect  the  delivery  tube  from  the 
flask  at  the  rubber  joint.  Collect  the  precipitate  on  a  small  filter, 
wash  it  once  with  water  and  then  while  still  moist  throw  the  pre- 
cipitate and  filter  back  into  the  test  tube,  in  which  has  been  placed 
some  powdered  potassium  chlorate.  Pour  upon  the  filter  and  pre- 
cipitate 10  cc.  of  concentrated  hydrochloric  acid.  Allow  to  stand 
in  a  cool  place  until  the  fumes  have  passed  off,  then  add  25  cc. 
of  hot  water,  filter  off  the  pulp,  etc.,  and  wash  with  hot  water. 


ANALYTICAL  METHODS  2O5 

Heat  the  filtrate  to  boiling  and  add  ammonia  until  the  solution  is 
slightly  alkaline.  Then  acidulate  with  a  few  drops  of  hydrochlor- 
ic acid,  add  10  cc.  of  a  10  per  cent,  solution  of  barium  chloride, 
also  brought  to  a  boil,  boil  for  a  few  minutes  and  stand  in  a  cool 
place  over  night.  Filter,  wash,  ignite,  and  weigh  as  barium  sul- 
phate. Multiply  this  weight  by  0.30895  for  calcium  sulphide, 
CaS,  or  by  0.13734  for  sulphur,  S. 

Notes. 

Instead  of  alkaline  lead  nitrate  solution,  a  solution  of  cadmium 
chloride  made  slightly  alkaline  with  ammonia  may  be  used  to  ab- 
sorb the  evolved  hydrogen  sulphide,  in  which  case  the  cadmium 
sulphide  precipitated,  may  be  collected  upon  a  previously  weighed 
filter  paper,  dried,  weighed  and  the  sulphur  calculated  from  this 
weight.  For  this  method  use  10  grams  of  cement  for.  the  sample 
and  fill  the  test  tube  two-thirds  full  of  a  solution  of  cadmium 
chloride,  made  by  dissolving  3  grams  of  cadmium  chloride  in  75 
cc.  of  water,  adding  ammonia  until  the  precipitate  at  first  formed 
redissolves  and  then  diluting  to  500  cc.  Proceed  as  usual.  Col- 
lect the  precipitate  of  cadmium  sulphide  upon  a  small  counterpois- 
ed filter,  or  better  in  a  Gooch  crucible  and  felt,  wash  with  water  to 
which  a  little  ammonia  has  been  added,  dry  at  100°  C.,  and  weigh 
as  cadmium  sulphide,  CdS.  The  weight  of  cadmium  sulphide 
multiplied  by  0.5000  gives  the  equivalent  amount  of  calcium  sul- 
phide. Calculate  the  percentage  and  report  as  such  or  merely  re- 
port as  sulphur.  If  the  former,  calculate  the  total  sulphur,  as 
found  by  either  of  the  methods  on  pages  59-60  to  calcium  sul- 
phate, by  multiplying  the  weight  of  the  barium  sulphate  by 
0.58565.  Now  multiply  the  percentage  of  calcium  sulphate  so 
found  by  0.41185  and  deduct  the  product  from  the  percentage  of 
lime  (as  found  by  precipitation  as  oxalate  in  the  general  scheme). 
The  difference  should  be  reported  as  calcium  oxide,  or  lime,  CaO. 
Multiply  the  percentage  of  calcium  sulphide  by  1.8872  for  its 
equivalent  in  calcium  sulphate  and  deduct  from  the  percentage 
of  total  sulphur  calculated  as  calcium  sulphate.  Report  the  dif- 
ference as  calcium  sulphate. 

Calcium  sulphide  may  also  be  determined  indirectly  by  deter- 
mining first  the  sulphur  present  as  sulphate  and  then  the  total 


2O6 


PORTLAND   CEMENT 


sulphur.  The  difference  will  represent  the  sulphur  present  as 
sulphide.  This  may  be  reported  either  as  CaS  or  as  S.  By  this 
method,  however,  errors  are  made  to  appear  as  CaS. 

Barium  sulphate  is  a  troublesome  precipitate  to  filter  as  it  is 
likely  to  run  through  the  paper.  For  this  reason  it  is  well  to  use 
a  double  paper.  Some  operators  use  a  Gooch1  crucible,  but  a 
device  suggested  by  Dr.  Porter  W.  Shimer,  of  Easton,  Pa.,  is 
still  handier.  It  is  shown  in  its  simplest  form  in  Fig.  48. -  It  con- 
sists of  a  glass  tube  cut  off  square  at  both  ends,  two  inches  long 


Fig.  48,  Shimer's  Filter  Tube. 

and  one  inch  in  internal  diameter.  The  edges  should  be  left 
sharp  and  not  rounded  in  the  flame.  In  the  bottom  of  the  tube  is 
a  rubber  stopper  fitted  with  a  glass  tube  for  attachment  to  the 
suction  flask.  On  the  stopper  when  inserted  into  the  tube  is  a 

1  See  page  184. 

^ Jour.  Amer.  Chem.  Soc.,  XXVII,  287.     Chemical  Engineer,  II.,  39. 


ANALYTICAL  METHODS  2O/ 

disk  of  piano  felt  3/16  mcn  thick,  fitting  closely  into  the  tube.  The 
filter  tube  is  now  ready  for  the  filter.  Take  unwashed  Swedish 
iilter  paper,  in  any  convenient  amount,  crush  it  into  a  ball  in  the 
hand  and  place  it  in  a  large  cereccne  hydrofluoric  acid  bottle  from 
which  the  upper  part  has  been  cut.  Add  hydrochloric  acid  (sp. 
gr.  1. 1 2  to  1. 1 8)  and  a  little  hydrofluoric  acid  and  stir  vigorously 
with  a  paraffin-coated  wooden  stirrer  until  the  paper  has  become 
a  mass  of  fine  soft  pulp.  Let  it  stand  a  few  minutes  and  then  add 
distilled  water.  In  preparing  a  filter,  pour  some  of  this  pulp  in 
the  beaker,  dilute  further  with  distilled  water  and  pour  enough  on 
the  felt,  under  suction,  to  make  a  filter  of  about  *4  inch.  Com- 
pact this  well  by  hard  stamping  with  a  stamper  made  from  a  solid 
rubber  stopper,  the  larger  end  of  which  is  only  a  little  smaller 
than  the  inner  diameter  of  the  tube.  A  hole  is  made  in  the  small 
end  of  the  stopper,  but  not  deep  enough  to  pass  quite  through  and 
a  short  glass  rod  inserted  in  this  for  a  handle.  Wash  the  filter 
two  or  three  times  with  water  and  then  filter  off  and  wash  the 
barium  sulphate,  using  suction.  This  may  be  done  rapidly  with- 
out fear  of  a  trace  of  the  precipitate  getting  into  the  filtrate. 

When  filtration  and  washing  are  complete,  turn  off  the  suction 
and  remove  the  filter  tube  from  the  stopper.  Take  the  stamper 
and  push  the  felt  up  until  the  filter  projects  beyond  the  tube, 
when  the  filter  may  be  detached  from  the  felt  by  a  pair  of  for- 
ceps ;  or,  if  preferred,  the  upper  end  of  the  tube  may  be  inserted 
into  the  weighed  crucible  and  the  felt  and  filter  may  be  pushed  at 
once  into  it,  when  the  felt  can  be  readily  removed  and  the  pre- 
cipitate and  filter  ignited.  Any  precipitate  adhering  to  the  sides 
of  the  tube  is  taken  along  by  the  outgoing  filter,  for  this  reason 
the  tube  should  be  of  uniform  diameter,  etc.  The  ash  of  these  fil- 
ters is  less  than  that  of  an  ordinary  filter  and  the  apparatus  gives 
excellent  results.  It  may,  of  course,  be  used  for  making  other 
filtrations,  but  is  particularly  well  adapted  for  use  with  barium 
sulphate. 

It  now  seems  to  be  pretty  well  established  that  it  is  not  neces- 
sary to  evaporate  to  dryness  and  separate  silica,  before  precipi- 
:ating  sulphur  with  barium  chloride,  provided  the  solution  is  suf- 
ficiently dilute  to  guard  against  separation  of  gelatinous  silica. 


2O8  PORTLAND  CEMENT 

LOSS  ON  IGNITION. 

Weigh  0.5  gram  of  cement  into  a  weighed  platinum  crucible, 
cover  with  a  lid,  and  heat  for  five  minutes  over  a  Bunsen  burner, 
starting  with  a  low  flame  and  gradually  raising  it  to  its  full 
height.  Then  heat  for  fifteen  minutes  over  a  blast  lamp.  Cool 
and  weigh.  The  loss  of  weight  represents  the  loss  on  ignition. 
This  loss  consists  mainly  of  combined  water  and  carbon  dioxide 
driven  off  by  the  high  temperature.  Some  chemists  report,  there- 
fore, as  "carbon  dioxide  and  water,"  or  having  found  the  carbon 
dioxide  subtract  the  percentage  from  that  of  the  "loss  on  igni- 
tion" and  call  the  remainder  "water  of  combination"  or  com- 
bined water.  As  both  sulphuric  acid  and  alkalies  are  driven  off, 
to  some  extent,  at  the  temperature  of  the  blast  lamp,  this  is  not 
strictly  correct  and  it  is  best  to  merely  report  as  "loss  on  igni- 
tion." This  loss  of  alkalies  is  shown  by  the  fact  that  if  the  cruci- 
ble lid  is  rinsed  off  with  distilled  water,  after  the  crucible  has 
been  ignited  and  weighed,  and  is  then  ignited  for  a  moment  to 
dry  it  and  placed  back  on  the  crucible,  the  weight  of  the  whole 
will  be  from  0.5  milligram  to  1.5  milligram  lighter,  showing  the 
condensation  of  the  alkalies  on  the  lid. 

In  conducting  the  ignition  it  is  best  to  place  the  crucible  with  its 
bottom  projecting  through  a  round  hole  in  a  piece  of  platinum 
foil,  which  in  turn  rests  upon  a  piece  of  asbestos  board  with  a 
slightly  larger  hole  cut  in  it.  The  flame  should  be  played  at  an 
angle  upon  the  bottom  of  the  crucible  so  that  the  products  of 
combustion  are  swept  away  from  it. 

DETERMINATION  OF  CARBON  DIOXIDE  AND 
COMBINED  WATER. 

Cements  contain  carbon  dioxide,  the  amount  varying  from  a 
mere  trace  in  a  fresh  well-burned  Portland  cement  to  a  large  per- 
centage in  natural  cements.  Combined  water  is  also  present  in 
cements,  the  amount  varying  as  does  the  carbon  dioxide  with  their 
age. 

Apparatus. 

For  carrying  out  the  determination  of  carbon  dioxide  and  com- 
bined water  at  the  same  time,  the  apparatus  designed  by  Dr.  Por- 


ANALYTICAL  METHODS 


2O9 


ter  W.  Shinier,  of  Easton,  Pa.,  for  carbon  combustions,  is  best 
suited. 

The  apparatus  as  used  for  carbon  dioxide  and  combined  water 
determinations  is  illustrated  in  Fig.  49.  It  consists  of  the  follow- 
ing parts : 

1.  The  aspirator  bottles,  a  and  a",  the  upper  a',  filled  with  dis- 
tilled water  and  the  tube  leading  to  the  lower  bottle  extending  to 
the  bottom  of  the  latter. 

2.  A  potash  bulb,  b,  containing  a  solution  of  caustic  potash  of 
1.27  sp.    gr.     The    form  of    bulb  shown    in  the    cut  is    Liebig's. 
Mohr's  or  any  other  form  will  do  as  well,  but  the  Liebig  bulb  is 
the  cheapest  and  answers  as  well  here  as  the  more   expensive 
forms. 


Fig.  49,  Apparatus  for  Determining  Carbon  Dioxide  and  Water  with  Shimer's  Crucible. 

3.  A  U-tube,  c,  filled  with  dried  granular  calcium  chloride.     A 
straight  calcium  chloride  tube  may  be  used  in  place  of  the  U-tube. 
It  takes  up  more  room,  however. 

4.  A  platinum  crucible,  d,  provided  with  a  water- jacketed  stop- 
per and  reservoir,  e,  for  supplying  water  to  this  latter.     Fig.  50 
shows  the  crucible  stopper,  etc.,  in  detail.   The  water-cooled  stop- 
per is  made  of  sheet  copper,  the  joints  being  brazed.   The  stopper 
should  be  made  as  nearly  perfectly  circular  as  is  possible,  and  free 
from  indentations  or  imperfections  in  the  brazing.     The  sides  of 

IJour.  Amer.  Chem.  Soc.,  XXI,  557  and  XXIII.,  227. 


2IO 


PORTLAND  CEMENT 


the  stopper  should  not  flare  more  than  the  sides  of  the  crucible 
at  the  top.  Too  much  flare  has  the  tendency  to  cause  the  stopper 
to  be  forced  out  when  under  pressure.  The  stopper  is  somewhat 
smaller  in  diameter  than  the  crucible  opening,  in  order  to  allow 
space  for  a  rubber  band.  This  band  may  be  obtained  of  stationers, 
and  is  of  black  rubber  ^4  to  *-2  inch  wide,  and  of  sufficient  length 
to  stretch  tightly  around  the  lower  part  of  the  stopper.  The  cruci- 
ble rests  with  its  bottom  through  a  circular  opening  in  a  piece  of 
3/16  inch  asbestos  board  which  in  turn  rests  upon  a  tripod. 


Fig.  50,  Shimer's  Water-Jacketed  Crucible. 

5.  A  small  U-tube,  f,  filled  with  dried  granular  calcium  chloride. 
The  best  form  is  that  shown,  provided  with  arms  and  glass  stop- 
cocks. 

6.  A  potash  bulb,  £,with  calcium  chloride  tube  attached.     The 
bulb  should  be  filled  with  caustic  potash  of  1.27  specific  gravity, 
and  the  tube  with  dried  granular  calcium  chloride. 

7.  A  guard  tube,  h,  filled  with  dried  granular  calcium  chloride. 

Testing  the  Apparatus. 

Fill  the  reservoir,  e,  with  boiling  water.  Half  fill  the  crucible 
with  freshly  ignited  asbestos,  and  close  it  with  the  water-cooled 
stopper.  A  little  powdered  soapstone  may  be  used  as  a  lubricant. 
In  putting  in  the  stopper  do  not  brace  the  thumb  against  the 
overflow  tube,  as  this  would  risk  bending  the  stopper  at  the  base 
of  the  overflow.  See  that  the  apparatus  is  perfectly  tight  by 
running  the  aspirator  and  pinching  the  tube  together  just  after 
the  potash  bulb. 


ANALYTICAL  METHODS  211 

Open  the  clamp  and  allow  water  to  run  out  of  the  stopper. 
Place  a  Bunsen  burner  under  the  crucible.  Open  the  clamp  be- 
tween the  lower  aspirator  bottle  and  the  potash  bulb,  b,  and  aspi- 
rate a  current  of  air  through'  the  apparatus  slowly  for  about 
twenty  minutes.  Detach  the  potash  bulb,  g,  and  the  calcium 
chloride  tube,  ff  and  weigh.  Again  connect  the  bulb  and  tube  in 
the  train  and  aspirate  air  slowly  through  the  apparatus  for 
another  twenty  minutes.  Detach  the  bulb,  gf  and  tube,  /,  and 
again  weigh  them.  This  weight  should  agree  to  within  0.0005 
of  the  former  weight  for  the  potash  bulb,  and  0.0003  f°r  the  cal- 
cium chloride  tube.  If  not,  after  making  sure  there  is  no  leakage 
in  the  apparatus,  repeat  the  test.  When  the  weights  agree 
within  the  limits  given,  take  the  last  pair  as  the  weights  of  the 
bulb  and  tube,  and  proceed  with  the  determination. 
The  Determination. 

Weigh  into  the  crucible  from  I  to  3  grams  of  cement,  cover 
with  ignited  asbestos  stopper  tightly.  Test  the  apparatus  and 
be  sure  there  is  no  leakage.  Place  the  Bunsen  burner  under  the 
crucible  after  starting  the  hot  water  to  flowing  through  the  stop- 
per. Cause  a  slow  current  of  air  from  the  aspirator  bottle  to  flow 
through  the  apparatus.  After  ten  minutes  replace  the  Bunsen 
burner  by  a  blast-lamp  and  continue  the  ignition  for  twenty  min- 
utes. Remove  the  lamp  and  aspirater  air  through  the  apparatus 
for  ten  minutes  longer.  Detach  the  potash  bulb,  g,  and  the  cal- 
cium chloride  tube,  f,  and  weigh.  The  increase  in  weight  of  the 
former  represents  the  carbon  dioxide,  CO2,  and  of  the  latter  water, 
H2O. 

Notes. 

In  this  method  the  combined  water  and  the  carbon  dioxide  are 
driven  out  of  the  cement  by  ignition ;  the  former  is  absorbed  in  a 
weighed  calcium  chloride  tube  and  the  latter  in  a  weighed  potash 
bulb.  The  increase  in  weight  of  the  tube  and  bulb  respectively 
represent  the  weight  of  combined  water  and  carbon  dioxide  in 
the  cement  sample.  The  air  entering  the  apparatus  for  the  pur- 
pose of  aspiration  is  purified  of  any  water  and  carbon  dioxide  it 
is  sure  to  contain  by  passing  through  the  caustic  potash  and  then 
over  calcium  chloride. 


212  PORTLAND  CEMENT 

To  make  the  upper  aspirator  bottle,  bore  a  hole  near  the  bot- 
tom of  a  five  pint  bottle  with  a  file  dipped  in  turpentine,  and  then 
slip  into  this  hole  a  bit  of  glass  tube  covered  with  an  inch  or  so 
of  soft,  thick-walled  rubber  tubing. 

To  fill  the  potash  bulbs  attach  a  short  piece  of  rubber  tubing 
to  one  end  and  dipping  the  other  end  in  the  caustic  potash  solu- 
tion contained  in  a  shallow  dish  apply  suction  to  the  rubber  tub- 
ing with  the  mouth.  When  the  bulbs  are  filled  to  the  proper 
height  (See  Fig.  49)  wipe  the  end  dry  inside  and  outside  with 
pieces  of  filter  paper. 

Instead  of  the  bulb,  b,  the  air  may  be  purified  of  any  carbon 
dioxide  it  contains  by  causing  it  to  bubble  through  caustic  potash 
solution  contained  in  two  4-ounce  wide-mouthed  bottles. 

Calcium  chloride  sometimes,  though  not  often,  contains  cal- 
cium oxide,  which  would  absorb  carbon  dioxide.  To  saturate  this, 
connect  the  apparatus,  leaving  out  the  potash  bulb,  f,  and  place 
a  small  piece  of  marble  in  the  crucible.  Now  heat  the  crucible 
with  a  blast  lamp  and  aspirate  air  slowly  through  the  apparatus. 
Then  take  the  marble  out  of  the  crucible  and  aspirate  air  for 
twenty  minutes  longer. 

The  potash  bulbs  and  IT-tube  should  be  weighed  as  follows  : 
Place  the  bulb  upon  one  balance  pan,  and  on  the  other  the  ap- 
proximate weight.  Stand  the  U-tube  in  the  balance  case.  Close 
the  door  and  do  not  open  it  for  exactly  twelve  minutes.  Then  fin- 
ish weighing  the  bulb  so  that  the  exact  result  is  obtained  in  fif- 
teen minutes  from  the  time  the  bulb  was  placed  on  the  pan.  Now 
remove  the  bulb  and  weigh  the  U-tube  quickly. 

When  not  attached  in  the  train  the  U-tube  should  have  its  stop- 
cocks turned  so  as  to  close  the  openings,  and  the  potash  bulb 
should  be  "capped"  with  short  pieces  of  rubber  tubing  containing, 
in  one  end,  bits  of  capillary  glass  tubing. 

If  the  cement  should  contain  any  appreciable  quantity  of  car- 
bonaceous matter,  such  as  unburned  coke,  this  would  be  burned 
to  carbon  dioxide  causing  high  results.  In  this  case  first  deter- 
mine the  carbon  dioxide  given  off  on  ignition.  Then  weigh  an- 
other sample  into  the  crucible,  add  a  little  hydrochloric  acid, 
filter  off  the  residue  on  ignited  asbestos/dry  at  100°  C,  and  deter- 


ANALYTICAL  METHODS 


213 


mine  the  carbon  dioxide  in  the  residue  as  before.  This  will  rep- 
resent the  carbon  dioxide  due  to  the  burning  of  the  organic  mat- 
teer.  The  difference,  of  course,  represents  the  carbon  dioxide 
present  in  the  cement  as  carbonate. 


Fig.  51,  Portable  Apparatus  for  Carbon  Dioxide  and  Water.     Front. 

A  U-tube,  containing  soda-lime,  may  replace  the  potash  bulb,  gf 
This  tube  should  be  similar  to  f,  and  provided  with  ground  glass 
stoppers.  About  an  inch  of  calcium  chloride  should  top  the  soda- 
lime  in  the  limb  next  the  guard  tube,  h. 

When  many  carbon  dioxide  determinations  have  to  be  made,  it 
will  be  found  convenient  to  arrange  the  apparatus  on  a  stand  as 
shown  in  Figs.  51  and  52.  Fig.  52  shows  the  front  of  the  appara- 
tus and  Fig.  52  the  reverse.  The  stand  consists  of  a  wooden  base 
i-il/2  inches  thick,  and  upon  this  is  mounted  an  upright  board. 
At  the  end  of  this  board  and  running  entirely  across  the  base  is 
fastened  another  upright  at  right  angles  to  the  first.  These  up- 


214 


PORTLAND   CEMENT 


rights  support  a  shelf  upon  which  rests  the  upper  aspirator  bottle 
and  the  reservoir  for  the  water  cooled  stopper.  The  upright  near- 
est the  tripod  should  be  protected  against  the  heat  of  the  blast 
lamp  by  covering  with  a  sheet  of  asbestos.  The  U-tubes,  etc.,  rest 
upon  shelves  as  shown.  The  manner  of  clamping  the  U-tubes 


Fig.  52,  Portable  Apparatus  for  Carbon  Dioxide  and  Water.     Back. 

to  the  board  is  also  shown  in  Fig.  53.    a   and  a"   (Fig.  53)   are 


Fig.  53,  Clamp  for  U-Tubes. 

aspirator  bottles ;  b  is  filled  with  soda-lime  and  c  with  calcium 
chloride;  d  is  Shimer's  special  form  of  water-jacketed  platinum 
crucible;  e  (Fig.  50)  is  filled  with  calcium  chloride,  /  with  soda- 
lime  topped  with  calcium  chloride,  and  g  with  calcium  chloride. 


ANALYTICAL  METHODS 


215 


DETERMINATION  OF  CARBON  DIOXIDE  ALONE. 

The  apparatus  just  described  for  carbon  dioxide  and  combined 
water  determinations  may,  of  course,  be  used  for  determining 
carbon  dioxide  only.  In  this  case  it  is  not  necessary  to  weigh  the 
calcium  chloride  tube,  f,  and  in  place  of  the  expensive  U-tube 
with  its  ground-glass  stop-cocks,  a  simple  straight  form  calcium 
chloride  tube  can  be  used  just  as  well.  Neither  is  it  necessary  to 
supply  the  stopper  with  hot  water,  and  an  empty  potash  bulb  can 
replace  the  calcium  chloride  tube  c.  The  determination  is  car- 
ried out  precisely  as  if  both  the  water  and  carbon  dioxide  were 
being  considered,  with,  of  course,  the  exception  of  not  weighing 
the  tube,  f,  at  the  end  of  the  operation.  If  the  stopper  is  wet 
with  the  finger  before  insertion  into  the  crucible,  it  will  be  found 
to  go  in  easier.  This  is,  of  course,  not  permissible  when  the 
water  also  is  determined. 


;l 

Fig.  54,  Apparatus  for  Determining  Carbon  Dioxide  by  Evolution  Method. 

Some  chemists  prefer  to  determine  carbon  dioxide  by  libera- 
ting this  constituent  with  hydrochloric  acid  and  absorbing  the 
evolved  gas  in  a  weighed  potash  bulb. 

For  carrying  out  the  determination,  refer  to  the  apparatus 
(Fig.  49),  for  determining  carbon  dioxide  and  combined  water. 


2l6  PORTLAND   CEMENT 

Omit  the  U-tube,  c,  and  substitute  for  the  crucible,  d,  a  100  cc. 
wide-mouthed  flask  provided  with  a  funnel  tube.  Follow  the 
flask  with  a  U-tube,  containing  sulphuric  acid  (sp.  gr.  1.84)  and 
this  by  the  U-tube,  f,  the  potash  bulb,  g,  and  the  guard  tube,  h. 

A  convenient  way  of  arranging  the  apparatus  is  shown  in  Fig. 
54.  a  is  filled  with  soda-lime ;  b  is  a  funnel  tube  with  ground- 
glass  stop-cock ;  c  the  100  cc.  flask ;  d  contains  sulphuric  acid ;  e 
and  g  calcium  chloride;  /  is  the  weighed  potash  bulb,  and  h  the 
aspirator  bottle. 

The  Determination. 

Weigh  into  the  flask,  c,  from  2  to  10  grams  of  cement,  tritu- 
rate with  water  until  all  tendency  to  set  has  ceased,  and  connect 
the  soda-lime  tube  a  with  the  funnel  tube.  Aspirate  a  few  liters 
of  air  through  the  apparatus,  disconnect  and  weigh  the  potash 
bulb  with  its  attached  calcium  chloride  tube.  Again  connect  the 
apparatus,  aspirate  another  two  liters,  and  again  weigh  the  pot- 
ash bulb  and  attached  calcium  chloride  tube.  If  the  first  and 
second  weights  agree  to  within  0.0005  grams  of  each  other,  run 
into  the  flask  50  cc.  of  dilute  hydrochloric  acid  and,  if  sul- 
phides are  present,  a  very  little  chromic  acid.  After  connect- 
ing the  bulb  and  tube  in  the  train,  and  when  action  ceases  apply 
heat  gradually  until  the  contents  of  the  flask  boil.  Connect  the 
soda-lime  tube  a  and  aspirate  air  slowly  through  the  apparatus. 
Turn  out  the  burner  and  aspirate  two  liters  more  of  air.  Dis- 
connect the  potash  bulb  and  calcium  chloride  tube  and  weigh.  The 
gain  in  weight  is  carbon  dioxide.  Divide  the  increase  by  the 
weight  of  the  sample  used  and  multiply  the  quotient  by  100,  for 
the  percentage  of  carbon  dioxide  in  the  cement. 

RAPID  DETERMINATION  OF  CARBON  DIOXIDE, 

The  Apparatus. 

When  rapid  determinations  of  carbon  dioxide  have  to  be  made, 
the  following  apparatus,  which  is  a  modification  of  Rose's  form, 
may  be  used  to  advantage.  It  consists  (Fig.  55)  of  a  small  50  cc. 
Erlenmeyer  flask,  a,  provided  with  a  two-hole  rubber  stopper. 
Through  one  hole  of  this  latter  passes  a  3-inch  calcium  chloride 
tube,  b,  and  through  the  other  a  piece  of  bent  glass  tubing,  c,  one 


ANALYTICAL  METHODS 


arm  of  which  reaches  nearly  to  the  bottom  of  the  flask,  the  other 
through  another  stopper  to  the  bottom  of  a  small  wide  tube,  d. 
This  latter  is  made  from  a  5-inch  test  tube.  Such  an  apparatus 
will  weigh  from  35  to  60  grams  according  to  the  skill  and  choice 
of  materials  with  which  it  is  made. 


Fig.  55,  Apparatus  for  Rapid  Determination  of  Carbon  Dioxide. 

The  Determination. 

Place  a  little  wool  or  cotton  in  the  bottom  of  the  calcium  chlor- 
ide tube  and  then  fill  the  tube  with  calcium  chloride.  Next  two- 
thirds  fill  the  tube,  d,  with  dilute  hydrochloric  acid,  and  weigh 
into  the  flask  from  2  to  3  grams  of  Portland  cement.  Moisten 
the  cement  thoroughly  with  water,  place  the  stopper  in  the  flask, 
cap  the  openings,  o  and  o" ,  with  pieces  of  rubber  tubing  closed  at 
one  end  with  bits  of  glass  rod,  and  set  in  the  balance  case.  After 
ten  minutes  weigh.  Now  attach  a  small  guard  tube,  filled  with 
calcium  chloride,  to  the  opening,  o',  and  after  uncapping,  o", 
suck  the  acid  from  the  tube,  d,  into  the  flask,  a.  As  soon  as  the 
acid  is  all  in  a,  close  o"with  the  finger  and  cap  quickly.  Remove 
the  guard  tube,  and  after  effervescence  ceases  place  the  apparatus 
on  a  hot  plate  until  the  contents  of  the  flask  begin  to  boil.  Re- 


2 1 8  PORTLAND   CEMENT 

move  from  the  hot  plate,  cap  the  opening,  o',  and  set  aside  until 
the  apparatus  cools  to  the  temperature  of  the  room.  Uncap  o", 
attach  the  guard  tube  to  this  opening  this  time,  uncap  o'  and  blow 
air  gently  through  the  apparatus  for  five  to  seven  minutes.  Cap 
the  openings,  place  in  the  balance  case,  and  after  ten  minutes 
weigh.  Always,  before  weighing,  uncap  either  o'  or  o"  for  a  few 
seconds  and  then  recap.  This  allows  the  pressure,  caused  by  the 
change  of  temperature,  to  adjust  itself.  The  loss  in  weight  rep- 
resents the  carbon  dioxide,  CO2,  in  the  cement.  Divide  the  loss 
by  the  weight  of  the  sample  and  multiply  the  result  by  100  for 
the  percentage. 

DETERMINATION  OF  HYGROSCOPIC  WATER, 

Weigh  5  grams  of  the  sample  upon  a  tared  watch  glass, 
spreading  the  former  over  the  latter  in  a  thin  layer  and  dry  for 
one  hour,  (or  until  it  ceases  to  loose  weight)  at  a  temperature  of 
ioo°-iio°  C.  Cool  in  a  disiccator  and  weigh.  The  loss  in 
weight  represents  "Hygroscopic  Water"  or  "water  below 
1 10°  C."  or  "H2O-no°." 

Notes. 

Instead  of  a  watch  glass  a  weighed  platinum  or  porcelain  cru- 
cible may  be  used  and  a  smaller  sample  (i  gram)  taken. 

Either  of  the  two  forms  of  air-bath  described  below  will  be 
found  useful  for  drying  the  sample.  The  first  can  be  procured 
of  any  dealer  in  chemical  apparatus  and  the  second  can  be  made 
from  "scraps"  around  the  laboratory. 

The  ordinary  air-bath  consists  of  a  copper  box,  provided  with 
a  hinged  door  in  front,  and  holes  for  the  insertion  of  thermom- 
eters and  the  escape  of  the  water  vapor,  in  its  top.  The  box  rests 
upon  iron  legs  and  is  heated  by  a  Bunsen  burner  underneath. 

Air-baths  are  usually  provided  with  false  bottoms  of  sheet  iron 
in  order  to  prevent  the  destruction  of  the  real  one  of  copper  by 
the  burner  flame.  Ic  is  necessary  to  control  the  temperature  of 
the  air-bath  by  a  thermometer  inserted  through  a  cork,  in  the 
opening,  in  the  top  of  the  oven.  The  required  temperature  can 
be  maintained  by  adjusting  the  stop-cock  of  the  gas  supply.  After 
the  gas  has  once  been  regulated  the  temperature  will  remain  con- 


ANALYTICAL  METHODS 


219 


slant  for  some  hours.  Gas  regulators,  called  "thermostats,"  can 
be  purchased  from  dealers  in  chemists'  supplies,  and  while  they 
are  liable  to  become  clogged  and  get  out  of  order,  they  still  are 
very  convenient  for  keeping  a  constant  temperature. 

The  author  recently  described  (in  the  Scientific  American,  vol. 
Ixxx,  p.  230)  a  form  of  drying  oven  which  he  has  used  success- 
fully in  his  laboratory  for  some  years.  It  is  non-corrosive,  simple 
and  cheap.  In  the  metal  ovens,  the  acid  fumes,  given  off  in 
"baking"  certain  substances,  attack  the  metal,  forming  a  scale 
which,  in  spite  of  care,  will  sooner  or  later  drop  in  some  sample 
or  dish  drying  in  the  oven.  Fig.  56  shows  the  oven.  Select  a 


Fig.  56,  Glass  Drying  Oven. 

large  glass  bottle  and  cut  off  the  bottom  by  making  a  mark  on  it 
with  a  file,  wrapping  two  strips  of  wet  paper,  one  a  little  above 
and  one  a  little  below  the  mark,  and  revolving  the  bottle  slowly 
and  evenly  while  the  tip  of  a  small  blowpipe  flame  or  small  flame 
from  a  blast  lamp  plays  on  the  space  between  the  paper.  A  crack 
will  start  in  a  few  minutes,  which  will  follow  the  flame  around 
the  bottle.  The  sharp  edges  should  be  smoothed  by  a  file  dipped 


220  PORTLAND  C£M£NT 

in  turpentine,  and  a  narrow  strip  of  asbestos  wound  around  the 
neck  for  a  handle.  The  upper  half  of  the  bottle  is  placed  upon  a 
sand-bath  or  hot  plate,  and  the  object  to  be  heated,  upon  a  support 
of  glass  or  porcelain,  raised  above  the  sand-bath  by  a  wire  bent  to 
form  a  tripod.  The  temperature  is  regulated  by  a  thermometer 
thrust  through  a  cork  in  the  mouth  of  the  bottle.  Large  grooves 
should  be  cut  lengthwise  along  the  cork  to  make  a  free  escape  for 
the  steam  and  vapors,  and  to  create  a  current  of  hot  air  through 
the  oven.  Both  this  and  the  other  form  of  air-bath  described 
should  be  set  in  a  corner  shielded  from  air  drafts.  If  this  is  done 
the  maintaining  of  a  constant  temperature  will  be  much  simplified. 

DETERMINATION  OF  ALKALIES. 

J.  Lawrence  Smith's  Method, 

Mix  4  grams  of  the  finely  ground  cement  with  I  gram  of  am- 
monium chloride  by  grinding  together  in  a  clean  agate  mortar 
placed  upon  a  sheet  of  black  glazed  paper.  Add  4  grams  of  cal- 
cium carbonate  free  from  alkalies,  and  transfer  the  mixture  to  a 
large  platinum  crucible  provided  with  a  closely-fitting  cover.  Heat 
gently  at  first,  over  a  Bunsen  burner,  then  gradually  raise  the 
temperature  to  a  full  red  heat  and  keep  so  for  an  hour.  Cool  the 
crucible,  and  if  loose,  transfer  the  sintered  mass  to  a  small  beaker 
or  better  a  platinum  dish.  Wash  the  crucible  and  lid  with  hot 
water  and  pour  into  the  dish  or  beaker.  Digest  the  contents  of 
the  beaker  until  the  sintered  mass  slakes  to  a  fine  powder. 

If  the  sintered  mass  is  not  easily  detached  from  the  crucible, 
put  the  crucible  into  the  beaker,  add  hot  water  and  digest  with 
heat  until  the  mass  slakes.  Remove  the  crucible  and  wash  it  off 
into  the  beaker.  Now  filter  into  another  platinum  dish  or  beaker 
and  wash  the  residue  with  water.  Add  1.5  grams  of  pure  ammon- 
ium carbonate,  evaporate  carefully  to  about  50  cc,  and  add  a  little 
more  ammonium  carbonate  and  a  few  drops  of  ammonia.  Filter 
on  a  small  filter  into  a  dish  of  platinum  or  porcelain.  Test  the 
filtrate  with  a  few  drops  of  ammonium  carbonate  solution  to 
make  sure  all  the  calcium  has  been  precipitated.  Evaporate  to 
clryness  and  ignite  at  a  barely  visible  red  until  all  the  ammonia  salts 
are  expelled  and  white  fumes  cease  to  come  off.  Cool,  dissolve 


ANALYTICAL  METHODS  221 

in  a  little  water,  add  a  few  drops  of  barium  chloride  solution,  and 
then  a  little  ammonium  carbonate  solution  and  ammonium  oxa- 
late  solution  and  ammonia,  and  filter  from  any  residue  that  may 
form.  Add  three  or  four  drops  of  dilute  hydrochloric  acid  to  the 
filtrate  and  evaporate  to  dryness  in  a  weighed  platinum  dish.  Ig- 
nite carefully  as  before  and  weigh  as  sodium  chloride  and  potas- 
sium chloride,  NaCl  +  KC1.  Dissolve  the  mixed  chlorides  in 
water  (they  should  be  soluble  without  residue),  and  add  to  the 
solution  an  excess  of  platinic  chloride  solution.  Evaporate  near- 
ly to  dryness  on  the  water-bath,  add  20  cc.  80  per  cent,  alcohol  and 
let  stand  until  the  sodium  salts  dissolve.  Filter  through  a  small 
filter  and  wash  the  precipitate  by  decantation  with  80  per  cent, 
alcohol,  until  the  washings  run  through  perfectly  colorless.  Dry 
the  filter  paper  to  drive  off  all  the  alcohol  and  then  dissolve  the 
small  amount  of  precipitate  on  it  by  washing  with  hot  water,  al- 
lowing the  washings  to  run  into  the  weighed  dish  containing  most 
of  the  potassium  platinic  chloride  precipitate.  Evaporate  off  the 
water.  Dry  at  135°  C.,  and  weigh  as  potassium  platinic  chloride, 
ICPtClfl.  Multiply  the  weight  by  0.19398  x'or  potassium  oxide, 
K2O.  To  calculate  the  sodium  oxide,  multiply  the  weight  of  the 
potassium  plantinic  chloride  by  0.30701  and  subtract  this  from  the 
wreight  of  the  residue  of  potassium  and  sodium  chloride ;  the  dif- 
ference multiplied  by  0.53076  gives  the  weight  of  the  sodium 
oxide,  Na2O. 

Notes. 

During  the  first  part  of  the  incineration  of  the  mixture  of  ce- 
ment, calcium  carbonate  and  ammonium  chloride  the  heat  should 
be  kept  low.  The  idea  is  not  to  volatilize  the  ammonium  chloride, 
"but  to  dissociate  this  into  ammonia  and  hydrochloric  acid  by  the 
heat.  The  latter  then  unites  with  the  calcium  carbonate  to  form 
calcium  chloride. 

If  the  dishes  are  removed  direct  from  the  water-bath  to  the 
flame  for  ignition  decrepitation  is  sure  to  result.  To  guard 
against  this  place  the  dish  in  the  air-bath  at  a  temperature  of  100° 
C.  and  gradually  raise  to  120°  C.,  and  then  ignite  over  a  moving 
flame. 

The  heating  must  not  be  too  strong  as  potassium  chloride  is 


222  PORTLAND  CKMENT 

volatile.  To  test  its  freedom  from  ammonia  salts,  the  residue  of 
mixed  chlorides,  after  weighing,  should  be  again  heated  and 
weighed,  to  see  if  further  loss  occurs. 

This  operation  should  be  repeated  until  the  weights  are  con- 
stant. 

DETERMINATION  OF  PHOSPHORIC  ACID. 

Weigh  5  grams  of  cement  into  a  dry  beaker  and  stir  with  15 
to  20  cc.  of  water  until  all  lumps  are  broken  up.  Add  from  30  to 
50  cc.  of  hydrochloric  acid  (sp.  gr.  1.20)  cover  with  a  watch-glass 
and  heat  until  the  cement  is  decomposed.  Remove  the  cover, 
evaporate  to  hard  dryness  on  the  hot  plate,  and  heat  for  from 
thirty  minutes  to  one  hour  longer.  Redissolve  in  30  cc.  of  hydro- 
chloric acid  (sp.  gr.  1.20)  and  evaporate  to  pasty  consistency. 
Add  30  cc.  of  nitric  acid  (sp.  gr.  1.42)  and  evaporate  to  15  cc. 
Dilute  with  30  cc.  of  water,  heat,  filter  through  a  small  filter  and 
wash.  Add  ammonia  until  a  slight  precipitate  forms,  and  then  3 
cc.  of  concentrated  nitric  acid.  The  solution  should  now  be  am- 
ber-colored. Add  80  cc.  of  molybdate  solution,  heat  to  80°  C., 
and  stir  for  five  minutes.  Let  the  solution  stand  one  hour.  Filter 
and  wash  well  with  acid  ammonium  sulphate  solution.  Dissolve 
the  precipitate  in  the  least  possible  quantity  of  dilute  ammonia, 
(1-5)  and  allow  the  solution  to  run  into  the  beaker  in  which  the 
precipitation  was  made.  Wash  the  paper  well  with  cold  water. 
The  filtrate  should  be  clear  and  colorless.  (If  cloudy  add  hydro- 
chloric acid  until  the  liquid  is  acid,  this  usually  precipitates  the 
phosphomolybdate,  then  four  or  five  drops  of  a  concentrated  so- 
lution of  citric  acid  and  finally  ammonia  until  strongly  alkaline).. 
To  the  filtrate  add  slowly  with  constant  stirring  an  excess  of  mag- 
nesia mixture.  Stir  for  five  minutes,  then  add  one-third  the  vol- 
ume of  the  solution  of  strong  ammonia  and  allow  to  stand  three 
or  four  hours.  Filter,  wash  with  a  mixture  of  water  1000  cc.^ 
ammonia  500  cc.,  and  ammonium  nitrate  150  grams,  dry,  ignite, 
and  weigh  as  Mg2P2O7.  To  convert  this  weight  to  phosphorus 
pentoxide,  P2O5,  multiply  by  0.63809. 

Notes. 

The  solutions  called  for  in  the  scheme  are  prepared  in  the  fol- 
lowing manner: 


ANALYTICAL  METHODS  .  223 

Molybdate  Solution:  Mix  in  a  beaker  20  grams  of  pure  molyb- 
dic  acid  with  80  cc.  of  cold  distilled  water  and  add  16  cc.  of  am- 
monia (sp.  gr.  0.90).  When  solution  is  complete,  filter  and  pour 
slowly  into  a  mixture  of  80  cc.  of  nitric  acid  and  120  cc.  of  water. 

Ammonium  Sulphate  Solution:  Add  15  cc.  of  ammonia  (sp. 
gr.  0.90)  to  1000  cc.  of  water  and  then  25  cc.  of  concentrated  sul- 
phuric acid  (1.84  sp.  gr.). 

Magnesia  Mixture:  Dissolve  n  grams  of  crystallized  magne- 
sium chloride  in  water  (or  2.2  grams  of  calcined  magnesia  in 
dilute  hydrochloric  acid  avoiding  an  excess),  filter,  add  28  grams 
of  ammonium  chloride,  70  cc.  of  ammonia  (sp.  gr.  0.96),  and 
enough  water  to  make  200  cc.  Filter  before  using. 

DETERMINATION  OF  MANGANESE. 

Colorimetric  Method* 

Stir  0.2  gram  of  cement  with  10  cc.  of  water  until  all  lumps  are 
"broken  up,  add  10  cc.  of  concentrated  nitric  acid  and  heat  until 
solution  is  complete.  Dilute  to  100  cc.,  in  a  graduated  flask,  after 
cooling.  Mix  thoroughly  and  measure  10  cc.  of  this  solution,  into 
a  small  beaker,  with  a  pipette.  Add  2  cc.  of  nitric  acid  (1.2  sp. 
gr.)  and  heat  to  boiling.  Remove  from  the  flame  and  add  0.5 
gram  of  lead  peroxide,  stir  and  boil  for  two  minutes.  Allow  to 
stand  some  time  and  filter  through  a  filter  made  of  ignited,  washed 
asbestos.  The  filtrate  is  caught  in  a  graduated  Nessler  tube  or 
cylinder  and  the  filter  is  washed  with  a  very  little  water.  The 
solution  and  washings  are  then  mixed.  Into  another  cylinder 
from  1-3  cc.  of  a  standard  solution  of  manganese  (made  by  dis- 
solving 0.0556  gram  of  crystallized  potassium  permanganate  in 
500  cc.  of  water.  Strength  I  cc.  =  0.00005  gram  MnO)  is  meas- 
ured and  the  two  cylinders  stood  side  by  side  and  viewed  horizon- 
tally —  not  vertically.  Water  is  then  added  to  the  standard  to 
make  it  match  the  other  tube.  The  height  of  the  liquid  in  the 
two  tubes  is  then  read  and  the  percentage  of  MnO  calculated  from 
the  formula 

a  X  B  X 


A  X  w 

When  a  =  number  of  cc.  of  standard  solution  placed  in  the  cyl- 
inder and  A  the  number  of  cc.  to  which  it  is  diluted  in  order  to 


224  PORTLAND  CEMENT 

produce  the  same  shade  as  the  cement  sample  diluted  to  B  cc. 
W  =  weight  of  sample  taken  or  0.2  gram.  It  may  be  necessary 
where  the  cement  is  high  in  manganese  to  use  a  smaller  sample 
than  0.2  gram. 

DETERMINATION  OF  TITANIUM. 

Colorimetric  Method  of  A.  Wetter. 

If  titanium  is  to  be  determined,  follow  closely  the  method  of 
analysis  outlined  on  page  170.  Purify  the  silica  with  hydroflu- 
oric acid  and  ignite  the  iron  and  alumina  precipitate  in  the  same 
crucible  with  the  residue  from  this  treatment.  Dissolve  the  pre- 
cipitate, after  weighing,  in  potassium  bisulphate  by  fusion,  and 
then  the  fused  mass  in  water,  acidified  with  sulphuric  acid.  Evapo- 
rate the  fused  mass  until  fumes  of  sulphuric  acid  come  off.  Di- 
lute, filter  and  saturate  the  filtrate  with  hydrogen  sulphide  gas. 
Filter  from  any  platinum  sulphide  and  boil  off  the  hydrogen  sul- 
phide in  a  current  of  carbon  dioxide.  Determine  the  iron  by  titra- 
tion  with  potassium  permanganate  as  described  on  page  192. 

Concentrate  the  solution,  after  the  titration  is  completed,  to 
50  cc.  and  transfer  to  a  50  cc.  Nessler  tube.  Add  2  cc.  of  3  per 
cent,  hydrogen  peroxide,  absolutely  free  from  fluorine.  This  pro- 
duces an  intense  yellow  color  which  is  proportional  to  the  amount 
of  titanium  present.  Compare  this  color  with  that  produced  by 
hydrogen  peroxide  upon  various  volumes  of  a  standard  solution 
of  titanium  prepared  as  follows :  Gently  ignite  potassium  titanic 
fluoride  and  weigh  0.6000  grams  of  this  into  a  platinum  crucible. 
Add  a  little  sulphuric  acid  and  water,  evaporate  to  dryness  and 
expel  the  acid  by  gentle  ignition.  Repeat  this  process,  and  then 
dissolve  in  a  little  concentrated  sulphuric  acid  and  dilute  to  200 
cc.  with  5  per  cent,  sulphuric  acid.  One  cc.  of  this  solution  is 
equivalent  to  o.ooi  gram  of  TiO2  or  to  0.2  per  cent,  when  a  half 
gram  sample  has  been  used.  In  comparing  the  colors  measure 
into  different  tubes  0.5  cc.,  i.o  cc.,  1.5  cc.,  etc.,  portions  of  the 
standard  titanium  solution,  dilute  to  the  mark,  and  add  2  cc.  of 
hydrogen  peroxide  to  each.  Compare  with  the  color  produced  by 
the  sample,  making  up  new  standards  when  the  color  lies  between 
two  of  the  above  tubes,  etc. 

The  method  is  accurate  to  about  o.oi  per  cent,  when  a  one-half 
gram  sample  is  taken. 


CHAPTER  X. 


THE  ANALYSIS  OF  CEMENT  MIXTURES,  SLURRY,  Etc, 

Since  the  success  of  cement-making  depends  primarily  upon 
the  proper  portion  of  carbonate  of  lime  to  silica  and  alumina  in 
the  cement  mixture,  it  is  highly  important  to  be  able  to  rapidly 
estimate  this  ratio.  If  the  materials  from  which  the  mixture  is 
made  are  of  normal  constitution  a  determination  in  it  of  the  cal- 
cium carbonate  alone  will  suffice  to  check  the  correctness  of  the 
mixture. 

For  rapidly  checking  the  percentage  of  calcium  carbonate,  two 
methods  are  in  general  use,  the  alkalimetric  method  in  which  the 
calcium  carbonate  is  decomposed  by  a  measured  quantity  of  stand- 
ard nitric  or  hydrochloric  acid  and  the  excess  of  acid  determined 
by  titration  with  standard  alkali,  and  the  indirect  gas  method  in 
which  the  carbonate  of  lime  is  decomposed  by  acid  and  the 
evolved  carbon  dioxide  gas  collected  in  a  suitable  apparatus  and 
measured ;  since  the  CO2  is  proportional  to  the  CaCO3,the  percent- 
age of  lime  can  be  calculated  from  the  volume  of  CO2.  For  the 
latter  method  the  Scheiblers  calcimeter  is  used.  Neither  of  these 
methods  gives  very  accurate  results,  and  when  the  exact  composi- 
tion of  the  mixture  is  desired  resort  must  be  had  to  one  of  the 
longer  gravimetric  methods  given  further  on. 

When  the  slurry  of  the  wet  process  is  analyzed  it  should  first 
be  evaporated  to  dryness,  then  finely  pulverized  in  a  mortar  and 
again  dried  for  half  an  hour  at  no0  C.  It  will  then  be  free  from 
moisture  and  ready  for  analysis. 

SAMPLING,  ETC. 

For  the  control  of  the  composition  of  the  mixture  of  raw  mate- 
rials it  is  usual  to  take  samples  at  certain  places  during  the  grind- 
ing. In  the  dry  process  this  is  usually  done  either  after  the  mate- 
rial leaves  the  ball  mills,  if  these  are  used  to  do  the  grinding,  or 
after  the  Griffin  mills,  if  they  are  installed  for  this  work.  Where 
tube  mills  follow  the  ball  mills  it  is  usual  to  further  check  the 
composition  of  the  raw  material  after  it  leaves  these.  The  sample 

8 


226  PORTLAND 

taken  from  any  of  the  above  sources  will  need  further  grinding 
but  it  is  not  usual  to  dry  it,  unless  a  complete  analysis  is  to  be 
made.  Since  either  of  the  rapid  schemes  given  below  are 
affected  by  the  fineness  to  which  the  sample  is  ground,  it  should 
be  prepared  the  same  way  each  time,  usually  by  passing  all  of  it 
through  a  loo-mesh  test  sieve.  In  the  writer's  laboratory  the 
sample  from  the  ball  mills  is  taken  by  an  automatic  sampler  which 
will  be  described  further  on,  and  brought  to  the  laboratory  in  a 
small  tin  bucket.  The  sample  is  spread  out  on  a  piece  of  paper, 
after  a  thorough  mixing  by  rolling  back  and  forth  on  the  paper, 
and  divided  into  15-20  squares  with  the  point  of  a  spatula.  Two  or 
three  grams  are  taken  from  each  of  these  squares  and  the  main 
sample  is  then  thrown  away.  The  sample  of  from  50-100  grams 
is  now  made  to  pass  a  loo-mesh  sieve,  using  a  large  wedgewood 
mortar  to  do  the  grinding.  The  finely  ground  sample  is  then 
mixed  and  10-20  grams  of  it  placed  in  a  coin  envelope  or  small 
bottle  and  taken  to  the  chemical  laboratory.  The  wedgewood 
mortar  answers  the  purpose  much  better  than  an  agate  one  would 
and,  with  the  soft  rock  of  the  Lehigh  District,  does  not  contami- 
nate the  sample  with  silica  to  an  amount  which  can  be  detected. 
The  following  sampler,  Fig.  57,  was  devised  by  the  writer  with 
the  assistance  of  Mr.  Owen  Hess,  Superintendent  of  the  Dexter 
Portland  Cement  Co.  It  consists  of  a  tin  cone,  of  the  dimensions 
shown,  having  a  rectangular  tin  tube  inserted  at  one  point  in  its 
sides.  The  cone  slips  into  a  piece  of  four-inch  pipe  which  in 
turn  revolves  in  a  rigid  pillow  block.  The  cone  is  revolved  by  the 
bevel  gear  arrangement  shown,  which  is  run  from  one  of  the  mill 
shafts  by  a  sprocket  and  chain,  so  as  to  make  two  or  three  revolu- 
tions per  minute.  The  sampler  is  placed  below  an  overhead  screw 
conveyor  carrying  the  ground  material  from  the  ball  mills  to  the 
tube  mill  bins.  A  hole  is  cut  in  this  conveyor  trough,  so  that  a 
stream  of  this  material  falls  into  the  cone,,  striking  the  side  of 
the  latter  about  2  inches  from  the  rim.  As  the  cone  revolves,  the 
material  falls  into  the  cone  and  passes  down  through  the  hollow 
shaft  into  a  pipe,  which  carries  it  back  into  the  main  elevator  or 
one  of  the  tube  mill  bins.  When,  however,  the  tube  comes  under 
the  stream,  it  is  deflected  out  of  its  course  for  a  moment  and  pass- 
ed through  this  tube  down  another  pipe  into  a  sample  bucket 


ANALYTICAL  METHODS 


227 


placed  at  a  convenient  place.  The  frequency  with  which  the  sam- 
ple is  taken  will  depend  on  the  number  of  revolutions  per  minute 
the  cone  makes.  The  amount  will  depend  on  the  width  of  the  in- 
serted tube  and  the  circumference  of  the  cone.  The  sampler 
works  well  except  when  the  raw  material  is  very  wet  when  the 
pipes  clog  up. 


Fig-  57>  Automatic  Sampler. 

In  hand  sampling  from  the  ball  mill,  care  must  be  taken  not  to 
get  a  false  proportion  of  fine  and  coarse  material  in  the  sample. 
The  best  place  to  sample  is  from  the  conveyor  leading  from  the 
mills,  using  a  scoop  made  by  tacking  a  piece  of  tin,  three  quarters 
of  the  way  around,  a  piece  of  board  1^2  inches  square  and  8  or  10 
inches  long  as  shown  in  Fig.  58.  Never  put  the  hand  inside  a 


Fig.  58,  Scoop  for  Sampler. 

screw  conveyor  while  revolving,  as  loss  of  the  member  may  result. 
A  sample  of  cement  rock-limestone  mixture,  after  leaving  the 
mills,  will  usually  contain  from  0.05  to  0.3  per  cent,  moisture. 
Even  in  wet  weather  when  the  dryer  was  being  pushed  to  its 


228  PORTLAND   CEMENT 

utmost  and  the  mills  were  having  trouble  with  the  wet  material 
I  have  seldom  seen  more  than  the  latter  figure  present,  so  that  for 
control  and  check  purposes  drying  of  the  sample  seems  unneces- 
sary. 

In  the  wet  process,  the  analytical  methods  for  checking  the 
composition  of  the  slurry  are  practically  the  same  as  in  the  dry, 
but  on  the  other  hand,  the  sampling  can  not  be  done  the  same  way 
and  the  sample  itself  must  be  freed  from  a  large  amount  of  water 
(50-60  per  cent.)  by  drying.  The  slurry  samples  are  usually  taken 
from  the  mixing  pits,  and  also  after  the  slurry  has  passed  through 
the  tube  mills,  either  from  the  discharge  of  the  mill  itself  or  else 
from  the  slurry  pits. 

The  methods  of  sampling  employed  by  the  chemists  at  the 
various  mills  differ  as  the  following  will  show : 

Mr.  W.  H.  Hitchcock,  of  the  Egyptian  Portland  Cement  Co., 
took  samples  from  the  mixing  pit,  by  means  of  a  pint  cup,  fasten- 
ed to  the  end  of  a  wooden  pole  by  means  of  a  wire.  It  is  put  in  the 
slurry  bottom  side  up,  pushed  down,  to  the  required  depth,  about 
the  middle  of  the  pit,  and  drawn  up.  As  the  pole  is  pulled,  the  cup 
rights  itself  and  fills.  Each  pit  holds  170  cu.  yds.  and  is  sampled 
in  20  places.  The  sample  is  then  put  in  a  miniature  tube  mill 
and  ground  for  10  minutes.  From  25-35  grams  of  this  sample 
are  spread  on  a  thin  piece  of  cardboard  and  dried  at  100%  C., 
after  which  it  is  ground  in  an  agate  mortar  when  it  is  ready  for 
the  check  determinations. 

Mr.  N.  S.  Potter,  Jr.,  of  the  Peninsular  Portland  Cement  Co., 
takes  his  sample  from  the  slurry  tanks,  which  are  16  ft.  deep,  by 
means  of  a  two-quart  tin  pail,  attached  to  the  end  of  a  pole  by  a 
common  harness  snap.  The  pail  is  pushed  down  into  the  slurry, 
bottom  up,  and  full  of  air.  At  the  desired  point  the  pole  is  given 
a  slight  jerk  uhen  the  pail  rights,  allow  the  air  to  escape  and 
fills  with  the  marl  or  slurry,  as  the  case  may  be.  The  sample  is 
then  spread  out  on  a  piece  of  paper  and  dried  on  the  hot  plate. 

Mr.  Frank  I.  Post,  of  the  Wolverine  Portland  Cement  Co.,  uses 
a  special  form  of  sampler,  consisting  of  a  cup  with  two  fly  valves, 
one  at  the  top  and  another  at  the  bottom,  attached  to  a  pole.  When 


ANALYTICAL  METHODS  22Q 

the  sampler  is  thrust  down  through  the  slurry,  both  valves  open 
and  the  marl  simply  runs  through  the  cup,  but  when  the  sampler  is 
raised  the  valves  shut,  thus  enclosing  a  sample  in  the  cup.  In 
removing  this  sampler  from  the  tank  care  must  be  used  not  to 
lower  it  at  all.  If  this  is  done,  the  valves  of  course,  open  and  the 
sample  previously  taken  is  lost,  and  in  its  place  will  be  a  new 
sample  from  the  point  of  lowering. 

Mr.  Homer  C.  Lask,  of  the  Omega  Portland  Cement  Co.,  also 
makes  use  of  a  bucket  with  a  valve  in  sampling  marl.  His  appa- 
ratus consists  of  a  heavy  iron  bucket,  three  inches  in  diameter 
and  nine  or  ten  inches  long.  It  has  a  valve  in  the  bottom,  which 
opens  as  the  bucket  sinks  through  the  marl,  but  closes  as  soon  as 
it  is  started  in  the  opposite  direction.  A  sample  can  thus  be  taken 
at  any  depth  desired.  The  sampler  is  attached  to  a  rope  and 
sinks  into  the  marl  by  its  own  weight.  It  is  withdrawn  by  means 
of  a  small  windlass.  From  three  to  five  samples  are  taken  from 
a  tank,  the  different  samples  mixed  together,  and  the  whole  taken 
as  the  tank  sample. 

The  slurry  is  sampled,  automatically,  as  it  leaves  the  tube  mill 
by  an  ingenious  device.  The  tube  mills  at  this  plant  have  a  cen- 
tral discharge  and  on  the  inner  surface  of  the  discharge  conduit 
is  attached  a  stout  cup,  of  about  I  cu.  in.  capacity,  with  its  open 
end  towards  the  stream  of  slurry  as  the  mill  makes  its  revolu- 
tion. The  cup  fills  as  it  passes  through  the  stream  of  slurry  and 
discharges  as  it  is  carried  over  the  top.  A  portion  of  the  dis- 
charge is  allowed  to  fall  into  a  small  trough,  down  which  it  flows 
into  a  bucket.  This  bucket  holds  about  four  pints  and  the  sam- 
pler is  so  gauged  that  the  former  will  fill  in  about  an  hour. 

Samples  of  slurry  and  marl  may  also  be  taken  by  agitating  the 
vat  or  tank  thoroughly  and  then  taking  two  or  three  small  samples 
from  the  elevator  or  pump  discharge  and  mixing  and  grinding.. 
In  order  to  correct  the  composition  of  slurry  found  to  be  under-  or 
over-clayed,  it  is  necessary  to  know  not  only  how  much  carbonate 
of  lime  it  contains,  but  also  how  much  water.  To  determine  the 
latter  the  usual  rule  is  to  evaporate  a  weighed  portion  of  the 
slurry  to  dryness  and  determine  the  loss  in  weight.  This  evapora- 
tion can  be  carried  on  most  rapidly  and  also  safest  in  the  "radia- 


230  PORTLAND 

tor."  This  consists  of  a  round  sheet  iron  box,  with  an  open  top 
and  bottom  flanged  on.  It  is  made  of  any  convenient  dimensions 
and  usually  with  its  diameter  at  the  top  a  little  larger  than  at  the 
bottom.  Convenient  dimensions  are  6  inches  deep,  5^  inches 
diameter  at  the  top  and  4^  inches  diameter  at  the  bottom.  The 
radiator  will  then  set  in  the  ring  of  a  five-inch  tripod.  The  sub- 
stance to  be  evaporated  is  held  on  a  triangle  support,  midway  be- 
tween the  top  and  bottom  of  the  box  and  made  of  heavy  copper  or 
iron  wire.  Fig.  59  shows  the  apparatus,  which  is  to  be  heated  by 
a  burner. 


Fig.  59,  Radiator  for  Drying  Slurry  Samples. 

Practically  the  same  results  can  be  arrived  at  by  using  a  round 
sheet  iron  cylinder,  6  inches  high  and  5  inches  in  diameter  with  a 
support  3  inches  from  the  bottom,  and  setting  over  the  hottest  part 
of  the  hot  plate.  An  ordinary  porcelain  dish  may  be  made  use  of 
to  hold  the  sample  but  a  flat  dish  of  tin  or  aluminum  will  serve 
the  purpose  better.  Not  only  because  greater  surface  is  exposed 
but  also  because  metal  is  a  better  conductor  of  heat  than  porce- 
lain. As  a  quick  test  to  determine  when  all  the  water  is  driven 
off,  hold  a  cold  watch  glass  over  the  dish  and  observe  if  any  mois- 
ture collects  on  it.  If  16.88  c.c.  of  slurry  are  taken  for  evapora- 
tion each  o.oi  gram  of  dried  residue  will  represent  the  number  of 
pounds  of  dried  slurry  in  a  cubic  yard  of  the  wet  slurry.  This 
amount  may  be  measured  by  means  of  a  small  pipette  made  to 
hold  exactly  this  amount  to  the  mark.  In  use  the  pipette  must  be 
washed  out  with  a  jet  of  water  from  a  wash  bottle.  Or  168.8 
c.c.  may  be  taken  when  o.i  gram  will  represent  pounds  per  cu. 
yard,  etc.  When  organic  matter  is  present  this  also  acts  as  a  dis- 
turbing element  in  determining  the  correctness  of  the  composition 


ANALYTICAL  METHODS 


231 


of  the  slurry.  If  constant,  allowance  can  usually  be  made  for  it, 
but  when  variable  the  best  plan  is  either  to  burn  this  off  or  else  run 
the  mix  by  a  ratio  of  lime  to  insoluble.1 

Mr.  A.  Lindteigen,  of  the  Peerless  Portland  Cement  Co.,  weighs 
the  dried  sample  into  a  small  iron  tray,  which  is  suspended  in  a 
larger  one  and  this  in  its  turn  is  covered  and  put  over  a  good  Bun- 
sen  burner  for  20  minutes.  In  this  way  over  three  quarters  of  the 
organic  matter  is  driven  off  without  decomposing  the  carbonate. 
This  also  puts  the  sample  in  such  a  condition  that  it  will  sink  in 
a  solution  of  hydrochloric  acid,  and  be  quickly  dissolved.  With- 
out this  baking  process  the  marl  used  by  this  company  will  float  on 
top  of  the  acid  and  even  shaking  and  boiling  will  dissolve  it- only 
with  difficulty.  The  baked  sample,  however,  is  very  hygroscopic 
and  takes  up  moisture  rapidly  from  the  air,  so  it  must  be  weighed 
quickly. 

RAPID  METHODS  FOR  CHECKING  THE  PERCENTAGE 
OF  CALCIUM  CARBONATE  IN  CEMENT  MIXTURES* 

By  Standard  Acid  and  Alkali* 

Phenolphthalein. 

Dissolve  i  gram  of  phenolphthalein  in  100  cc.  of  alcohol  (50 


Fig.  60,  Phenolphthalein  Dropper. 

per  cent.).     Keep  in  a  small  bottle  provided  with  a  perforated 
stopper  through  which  passes  a  small  pipette,  made  from  a  piece 

i  See  chapter  IV. 


232  PORTLAND   CEMENT 

of  5  inch  narrow  bore  glass  tubing  by  drawing  out  one  end  to  a 
fine  opening,  and  blowing  a  bulb  in  the  other,  Fig.  60. 
One  drop  of  this  solution  is  sufficient  for  a  determination. 

Standard  Alkali. 

In  order  to  prepare  standard  alkali  of  exactly  2/5  N  strength 
it  is  necessary  to  first  prepare  a  standard  solution  of  some  acid, 
preferably  of  sulphuric,  because  of  the  ease  with  which  this  can 
be  standardized  by  precipitation  with  barium  chloride.  To  pre- 
pare this  standard  acid,  measure  out  with  a  burette  11.2  cc.  of 
concentrated  sulphuric  acid  (1.84  sp.  gr.)  and  dilute  to  one  liter. 
Shake  well  and  measure  into  each  of  two  small  beakers  10  cc.  of 
this  sulphuric  acid  and  dilute  to  100  cc.  Add  a  few  drops  of 
hydrochloric  acid,  heat  to  boiling,  and  precipitate  the  sulphuric 
acid  with  barium  chloride.  Let  the  precipitate  stand  over  night, 
then  filter  through  a  double  filter  (or  preferably  the  Shimer  fil- 
ter3), wash  with  hot  water,  ignite  and  weigh.  Calculate  the  quan- 
tity of  this  acid  equivalent  to  10  cc.  of  2/nN.  sulphuric  acid  in  the 
following  manner.  Ten  cc.  of  2/5  N.  sulphuric  acid  should  give 
0.467  grams  of  BaSO4.  If  the  average  weight  of  both  precipitates 
is  a  gram,  then  letting  x  represent  the  number  of  cubic  centi- 
meters containing  0.467  grams  of  BaSO4, 

4.67 
o  467  :  a  :  :  x  :  10  or  x  = 

a 

Hence  — — cc.  of  our  standard  acid  will  be  equivalent  to  10  cc. 

of  2/5  N.  acid.  This  should  be  marked  on  the  bottle  and  the  solu- 
tion put  away  in  a  dark  cool  place  for  use  at  some  future  time. 
To  prepare  the  standard  alkali,  dissolve  175  grams  of  caustic 
soda  in  eight  liters  of  distilled  water  in  a  2-gallon  bottle  (which 
usually  holds  9  liters)  and  mix  well  by  shaking.  Now  measure 
into  each  of  two  beakers  the  quantity  of  our  standard  sulphuric 
acid  equivalent  to  10  cc.  of  normal  acid,  and  after  adding  a  drop 
of  phenolphthalein  solution,  run  in  the  sodium  hydroxide  solution 
from  a  burette  until  the  solution  turns  purple-red.  The  two  titra- 
tions  should  check  exactly.  If  not,  repeat  until  they  do.  Now 
dilute  the  caustic  soda  solution  so  that  it  is  exactly  2/5  Normal. 

1  See  page  206. 


HF 

UNIVERSITY 

OF 


ANALYTICAL  METHODS    "  233 


The  number  of  cubic  centimeters  of  water  necessary  to  add  to 
the  caustic  soda  solution  may  be  found  by  the  formula 


(TT-) 


xc 


when  b  =•  cc.  soda  required  to  neutralize  the  equivalent  of  10  cc. 
of  -/ '5  N.  acid  and  C  ^quantity  of  caustic  soda  solution  still  left 
in  the  bottle. 

Example  of  the  preparation  of  the  standard  -/.  N.  alkali. 

Weight  of  ist  BaSO4  precipitate -4975 

"  2nd     "  "         -49^7 

Average .4981 

Therefore  — —  =9.38  cc.  of  the  acid,  are  equivalent  to  10  cc. 

of  2/3N  acid. 

Now  9.38  cc.  of  the  above  acid  require  8.7  cc.  of  caustic  soda, 
as  determined  by  duplicate  titrations.  As  we  have  used  20  cc.  of 
our  caustic  soda  we  will  have  in  the  bottle  8000-20  =17980  cc. 

and  hence  we  must  add  to  this  (  -      —  i )  7980  or  1 1 89  cc.     Since 

\  o.  7          / 

our  bottle  will  only  hold  9  liters  it  will  probably  be  better  to  draw 
off  exactly  i  litre  when  the  amount  to  be  added  to  the  remainder 

will  be  (  - —  —  i )  6980  or  1040  cc.     We  therefore  measure  out  this 

quantity  and  add  it  to  the  contents  of  the  bottle. 

The  standard  caustic  soda  solution  should  now  be  checked 
against  the  acid  and,  if  not  of  correct  strength,  water  must  be 
added,  as  indicated,  until  it  is  exactly  2/5  N.  strength. 

One  cc.  of  this  solution  is  equivalent  to  exactly  0.020  grams  of 
CaCO3,  or  2.0  per  cent,  where  a  one  gram  sample  is  used.  A 
two  gallon  bottle  of  standard  alkali  will  make  at  least  2000  deter- 
minations so  it  pays  to  make  it  of  correct  strength  and  save  calcu- 
lations 

Standard  Acid. 

Take  the  specific  gravity  of  a  bottle  of  hydrochloric  acid,  using 
a  hydrometer  for  the  purpose.  Refer  to  the  table  of  specific 
gravities  of  hydrochloric  acid  given  below  and  calculate  from  this 
the  quantity  of  acid  necessary  to  contain  97.0  grams  of  HC1. 
Measure  this  quantity  of  the  acid  into  a  liter  flask  and  dilute  to 
the  mark,  pour  into  an  eight  liter  bottle  and  add  seven  liters  of 


234 


PORTLAND   CEM£NT 


water,  measuring  with  the  flask.  Mix  the  contents  of  the  bottle 
well  by  shaking.  Ten  cc.  of  this  solution  should  be  equivalent  to 
from  8-1  to  8-5  cc.  of  the  2/5  N.  alkali  when  checked  by  adding  a 
drop  of  phenolphthalein  solution  and  running  in  the  alkali  to  a 
purple-red  color.  If  its  value  does  not  lie  between  these  figures 
add  acid  or  water  to  make  it  of  this  strength. 

TABLE  XXII. — SPECIFIC  GRAVITIES  OF  HYDROCHLORIC  ACID. 


Sp.  gr.  at 

15°  C. 

Degrees 
Baume\ 

Degrees 
Twadd'l. 

Per  cent, 
of  HC1. 

Grams  of  HC1 
in  i  liter. 

Correction  of 
the  sp.  gr. 
for  ±  i°  C. 

1.005 

0.7 

I 

1.  12 

11.32 

0.0006 

1.  010 

1.4 

2 

2.12 

21-45 

O.OOO6 

1.015 

2.1 

3 

3.12 

31.67 

0.0006 

1.020 

2.7 

4 

4.11 

41.99 

0.0006 

1.025 

3-4 

5 

5-iT 

52.41 

O.OOO6 

1.030 

4.1 

6 

6.II 

62.93 

0.0006 

i-  °35 

4-7 

7 

7.10 

73-55 

0.0006 

1.040 

5-4 

8 

8.10 

84-27 

O.OOO6 

1.045 

6.0 

9 

9.10 

95-09 

O.OOO6 

1.050 

6-7 

10 

10.09 

106.01 

0.0006 

1-055 

74 

ii 

11.09 

117.02 

O.OOO6 

i.  060 

8.0 

12 

12.09 

128.14 

O.OOO6 

1.065 

8.7 

13 

13.08 

139.36 

0.0006 

1.070 

9-4 

14 

14.08 

150.68 

0.0006 

1.075 

IO.O 

15 

15-08 

162.10 

0.0006 

1.080 

10.6 

16 

16.07 

173-63 

0.0006 

1.085 

II.  2 

17 

17.07 

185.24 

O.OOO6 

1.090 

11.9 

18 

18.07 

196.96 

0.0006 

!-095 

12.4 

19 

19.07 

208.78 

0.0006 

1.  100 

13.0 

20 

20.06 

220.70 

O.OOO6 

1.105 

13.6 

21 

21.06 

232.68 

0.0006 

I.  IIO 

14.2 

22 

22.06 

244.80 

O.OOO6 

I.HS 

14.9 

23 

23-05 

257-02 

0.0006 

I.I2O 

15-4 

24 

24.05 

269.34 

0.0006 

I.I25 

16.0 

25 

25-05 

281.76 

O.OOO6 

I.I30 

16.5 

26 

26.04 

294.  28 

0.0006 

I.I35 

17.1 

27 

27.04 

306.90 

O.OOO6 

I.I40 

17.7 

28 

28.04 

319.62 

O.OOO6 

I.I45 

18.3 

29 

29.03 

332-44 

0.0006 

I.I50 

18.8 

30 

30.03 

345-36 

0.0006 

I-I55 

19.3 

31 

31.03 

358.34 

0.0006 

1.160 

19.8 

32 

32.02 

371-44 

O.OOO6 

1.165 

20.3 

33 

33-02 

384.64 

O.ooo6 

1.170 

20.9 

34 

34-02 

397-94 

O.OOO6 

I.I75 

21.4 

35 

35-01 

411-34 

O.OOO6 

1.180 

22.O 

36 

36.01 

424.84 

0.0006 

1.185 

22.5 

37 

37.01 

438.44 

O.OOO6 

1.190 

23.0 

38 

38.01 

452.14 

0.0006 

I-I95 

23-5 

39 

39.00 

466.00 

o  .0006 

1.200 

24.0 

40 

40.00 

479-84 

0.0006 

ANALYTICAL,  METHODS  235 

Example  of  the  preparation  of  the  standard  acid. 

On  testing  a  bottle  of  hydrochloric  acid  its  specific  gravity  is 
found  to  be  1.195°  c-  at  23°  C.  Correcting  this  to  15°  C.  we 
have  1.195  +(23  —  15)  X  0.0006  =  1.1998,  or  practically  1.20  sp. 
gr.  at  15°  C.  Hydrochloric  acid  of  1.20  sp.  gr.  contains  479.84 
grams  of  HC1  per  litre  or  0.480  grams  per  cubic  centimeter. 

Therefore  — —  or  202  cc.  will  contain  97  grams  of  HC1,  hence 

we  measure  out  this  quantity  of  acid  and  dilute  to  eight  liters. 

Standard  Sample. 

A  standard  sample  of  the  raw  material  is  necessary  to  stand- 
ardize the  acid  and  alkali  for  actual  use.  This  sample  should  be 
ground  in  the  same  manner  as  the  daily  run  of  samples  to  be 
checked  by  the  acid  and  alkali.  It  should  all  pass  a  loo-mesh 
sieve  and  be  freed  from  hygroscopic  moisture,  by  drying  for  some 
hours,  at  110°  C.  Three  or  four  pounds  of  this  sample  should 
be  prepared  and  kept  in  air-tight  jars  or  bottles.  A  small  sample 
(one  or  two  ounces)  of  this  should  be  placed  in  a  two  ounce  bot- 
tle and  stoppered  with  a  rubber  cork  when  not  in  use.  This  small 
sample  can  then  be  re-dried  for  an  hour  at  ioo°-no°  C.  and  used 
for  standardizing,  avoiding  the  frequent  opening  and  mixing  of 
the  contents  of  the  large  jars  or  bottles. 

After  drying,  the  standard  sample  should  be  carefully  analyzed. 
It  should  contain  approximately  the  quantity  of  carbonate  of 
lime  which  it  is  desired  to  have  in  the  mix,  and  the  amount  of 
magnesia  should  also  be  normal.  When  the  magnesia  varies  at 
different  times  fresh  standard  samples  should  be  prepared  to  con- 
tain these  varying  percentages  of  magnesia;  otherwise  the  lime 
will  be  reported  too  high. 

Standardising  the  Acid. 

Weigh  one  gram  of  the  standard  sample  into  a  600  cc.Erlenmeyer 
flask  and  run  in  from  a  pipette  50  cc.  of  standard  acid.  Close  the 
flask  with  a  rubber  stopper,  having  inserted  through  it  a  long- 
glass  tube  30  inches  long  and  about  %-inch  internal  diameter. 
Heat  the  flask  on  a  wire  gauze  over  a  burner  as  shown  in  Fig.  61 
until  steam  just  begins  to  escape  from  the  upper  end  of  the  tube. 
The  heating  should  be  so  regulated,  that  the  operation  requires 


236 


PORTLAND  CEMENT 


very  nearly  two  minutes,  from  the  time  the  heat  is  applied,  until 
steam  issues  from  the  tube.  Remove  the  flask  from  the  heat,  as 
soon  as  the  steam  escapes  from  the  tube,  and  rinse  the  tube  into 
the  flask,  in  the  following  manner.  Rest  the  flask,  still  stoppered, 
on  the  table  and  grasp  the  tube  between  the  thumb  and  forefinger 
of  the  left  hand.  Direct  a  stream  of  cold  water,  from  a  wash 
bottle  in  the  right  hand,  down  the  tube,  holding  the  latter  inclined 


Fig.  61,  Apparatus  for  Determining  Calcium  Carbonate  with  Acid  and  Alkali. 

at  an  angle  of  45°,  and  rolling  the  flask  from  side  to  side  on  the 
table,  in  sweeps  of  two  or  three  feet,  by  twirling  the  tube  between 
the  finger  and  thumb.  Unstopper  the  flask  and  rinse  off  the  sides 
and  bottom  of  the  stopper,  into  the  flask,  and  wash  down  the  sides 
of  the  latter.  Add  a  drop  or  two  of  phenolphthalein  and  run  in 
the  standard  alkali,  from  a  burette,  until  the  color  changes  to 
purple-red.  This  color  is  often  obscured  until  the  organic  matter 
settles,  so  it  is  necessary  to  hold  the  flask  to  the  light  and  observe 
the  change  by  glancing  across  the  surface.  A  little  practice  will 
easily  enable  the  operator  to  carry  on  the  titration  with  accuracy 
and  precision. 

If  the  standard  sample  contains  L  per  cent,  carbonate  of  lime 
and  d  cc.  of  alkali  are  required  to  produce  the  purple-red  color, 
then  to  find  the  carbonate  of  lime  in  other  samples  it  is  only  nee- 


ANALYTICAL  METHODS 


237 


essary  to  subtract  the  number  of  cubic  centimeters  of  alkali  re- 
quired in  their  case  from  d,  multiply  the  difference  by  2  and  add 
to  L  for  the  percentage  of  carbonate  of  lime  in  them;  or  if  the 
number  of  cc.  is  greater  than  d,  subtract  d  from  this  number,  mul- 
tiply by  2  and  subtract  from  L,  for  the  carbonate  of  lime. 

In  order  to  avoid  all  calculations  prepare  a  table  giving  the 
various  percentages  of  carbonate  of  lime  corresponding  to  differ- 
ent quantities  of  alkali. 

Example  of  Such  a  Table:  Suppose  the  standard  sample  con- 
tains 75.0  per  cent,  carbonate  of  lime  and  4.6  cc.  of  standard  al- 
kali are  required  to  produce  a  purple-red  color.  Then  since  each 
cc.  of  alkali  is  equivalent  to  0.02  grams  or  2  per  cent,  of  carbon- 
ate of  lime  4.5  cc.  alkali  would  represent  75.2  per  cent,  carbonate 
of  lime  and  4.4  cc.  alkali  would  be  equivalent  to  75.4  per  cent, 
carbonate  of  lime.  Similarly  4.7  cc.  alkali  are  equal  to  74.8  per 
cent,  carbonate  of  lime.  So  we  see  the  lime  progresses  by  0.2  per 
cent,  for  each  decrease  of  o.i  cc.  alkali  and  we  can  quickly  write 
the  following  table : 


cc. 

Alkali. 

Per  cent. 

CaCO3. 

cc. 

Alkali. 

Per  cent. 
CaC03. 

cc. 
Alkali. 

Per  cent. 
CaCO*. 

3-8 

76.6 

4-5 

75-0 

5-2 

73-8 

3.85 

76.5 

4-55 

75-1 

5-25 

73-7 

3-9 

76.4 

4.6 

75-0 

5-3 

73-6 

3-95 

76.3 

4-65 

74-9 

5-35 

73-5 

4.0 

76.2 

4-7 

74.8 

5-4 

73-4 

4-05 

76.1 

4-75 

74-7 

5-45 

73-3 

4.1 

76.0 

4-8 

74-6 

5-5 

73-2 

4-15 

75-9 

4-85 

74-5 

5-55 

73-  r 

4.2 

75-8 

4-9 

74-4 

5-6 

73-o 

4-25 

75-7 

4-95 

74-3 

5.65 

72.9 

4-3 

75-6 

5-0 

74-2 

5-7 

72.8 

4-35 

75-5 

5-o 

74.1 

5-75 

72.7 

4-4 

75-4 

5-i 

74.0 

5-8 

72.6 

4-45 

75-3 

5-15 

73-9 

5.85 

72-5 

23**  PORTLAND   CEMENT 

Determination. 

Weigh  I  gram  of  the  sample,  which  has  been  ground  to  pass  a 
loo-mesh  sieve,  into  the  flask,  add  50  cc.  of  the  standard  acid  and 
proceed  as  directed  under  standardizing  the  acid.  The  percent- 
age of  carbonate  of  lime  may  be  found  from  the  number  of  cc. 
of  alkali  used  either  from  the  preceding  table  or  by  the  formula 

%  CaC03  =  L  —  (d  —  S)  X  2 

Where  L  and  d  have  the  same  values  as  in  the  paragraph  on 
"Standardizing  the  Acid"  and  5  represents  the  number  of  cubic 
centimeters  required  for  the  sample  whose  composition  is  de- 
sired. If  4.25  cc.  of  alkali  are  required  then  the  sample  contains 
75  —  (4.6  —  4.25)  X  2  =  75.7  per  cent,  carbonate  of  lime. 

NOTES. 

The  process  depends  upon  the  decomposition  of  calcium  car- 
bonate by  a  measured  quantity  of  standard  alkali  in  excess  of  that 
required  by  theory  and  then  determining  the  excess  acid  by  titra- 
tion  with  standard  alkali. 

CaC03  -1-  2HC1  =  CaCl2  +  H2O  +  CO2 
ioo. i  36.45 

HC1  -f  NaOH  =  NaCl  -f  H2O 
36.45         40.05 

Hence,  I  cc.  of  2/5  normal  acid  will  decompose  0.02  grams  of 
CaCO3  and  I  cc.  of  2/5  normal  acid  will  neutralize  as  much  acid 
as  0.02  grams  of  CaCO3. 

Phenolphthalein  is  a  very  delicate  indicator.  It  is,  however, 
very  susceptible  to  carbon  dioxide  and  the  solution  must  be  freed 
from  the  latter  by  boiling  whenever  this  indicator  is  used.  It  is 
also  useless  in  the  presence  of  free  ammonia  or  its  compounds. 
The  addition  of  a  few  drops  of  the  indicator  to  an  acid  or  neutral 
solution  shows  no  color,  but  the  faintest  excess  of  caustic  alkali 
gives  a  sudden  change  to  purple-red.  Methyl  orange  may  be  used 
in  place  of  phenolphthalein.  While  not  so  delicate  it  possesses 
certain  advantages  over  the  latter.  It  can  be  used  in  the  cold 
with  carbonates,  and  its  delicacy  is  not  impaired  by  the  presence 
of  ammonia  or  its  salts.  A  convenient  strength  for  the  methyl- 
orange  indicator  is  o.i  gram  of  the  salt  to  ioo  cc.  of  water.  One 
drop  of  this  solution  is  sufficient  for  ioo  cc.  of  any  colorless  solu- 
tion. Alkaline  liquids  are  faintly  yellow  with  methyl-orange  and 


ANALYTICAL  METHODS  239 

acid  ones  are  pink.  Of  the  two  indicators,  however,  phenol- 
phthalein  is  much  to  be  preferred  for  this  work,  as  the  carbon 
dioxide  has  all  been  boiled  off  the  acid  and  provided  the  alkali  is 
properly  kept,  the  amount  in  this  is  constant  and  hence  exercises 
the  same  influence  all  the  time. 

Standard  2/5  N  caustic  soda  may  be  prepared,  however,  free 
from  carbon  dioxide,  by  the  following  method:  Take  about 
twice  the  quantity  of  caustic  soda  required  for  the  standard  solu- 
tion, dissolve  in  water  and  add  25  grams  of  freshly  slaked  lime 
made  into  a  milky  paste  with  water.  Boil  for  10  or  15  minutes 
and,  when  cool  enough  to  avoid  cracking  the  latter,  pour  into  a 
five-pint  bottle.  Add  water  enough  to  nearly  fill  the  bottle,  stop- 
per, shake  and  let  stand  over  night  to  settle.  In  the  morning, 
siphon  off  the  clear  liquid  and  make  up  to  five  or  six  liters.  Run 
against  the  standard  sulphuric  acid  solution  and  dilute  as  directed 
above  for  the  preparation  of  2/5  N  alkali. 

As  a  preliminary  standard  for  the  preparation  of  the  2/5  N  al- 
kali, hydrochloric  acid  may  be  used  instead  of  sulphuric  acid.  It 
is  more  troublesome  to  standardize,  however.  Prepare  the  2/5 
normal  hydrochloric  acid  as  directed  in  the  scheme  and  standard- 
ize gravimetrically  as  follows: 

To  any  convenient  quantity  of  the  acid  to  be  standardized,  add 
solution  of  silver  nitrate  in  slight  excess,  and  2  cc.  pure  nitric  acid 
(sp.  gr.  1.2).  Heat  to  boiling  point,  and  keep  at  this  temperature 
for  some  minutes  without  allowing  violent  ebullition,  and  with 
constant  stirring,  until  the  precipitate  assumes  the  granular  form. 
Allow  to  cool  somewhat,  and  then  filter  through  asbestos.  Wash 
the  precipitate  by  decantation,  with  200  cc.  of  very  hot  water,  to 
which  has  been  added  8  cc.  of  nitric  acid  and  2  cc.  of  dilute  solu- 
tion of  silver  nitrate  containing  I  gram  of  the  salt  in  100  cc.  of 
water.  The  washing  by  decantation  is  performed  by  adding  the 
hot  mixture  in  small  quantities  at  a  time,  beating  up  the  precipi- 
tate well  with  a  thin  glass  rod  after  each  addition.  The  pump  is 
kept  in  action  all  the  time ;  but  to  keep  out  dust  during  the  wash- 
ing, the  cover  is  only  removed  from  the  crucible  when  the  fluid  is 
to  be  added. 

Put  the   vessels   containing  the   precipitate   aside,   return   the 


240  PORTLAND  CEMENT 

washings  once  through  the  asbestos  so  as  to  obtain  them  quite 
clear,  remove  from  the  receiver,  and  set  aside  to  recover  the  silver. 
Rinse  the  receiver  and  complete  the  washing  of  the  precipitate 
with  about  200  cc.  of  cold  water.  Half  of  this  is  used  to  wash  by 
decantation  and  the  remainder  to  transfer  the  precipitate  to  the 
crucible  with  the  aid  of  a  trimmed  feather.  Finish  washing  in  the 
crucible,  the  lumps  of  silver  chloride  bejng  broken  down  with  a 
glass  rod.  Remove  the  second  filtrate  from  the  receiver  and  pass 
about  20  cc.  of  alcohol  (98  per  cent.)  through  the  precipitate. 
Dry  at  from  140°  to  150°.  Exposure  for  half  an  hour  is  found 
more  than  sufficient  at  this  temperature,  to  dry  the  precipitate 
thoroughly.  The  weight  of  silver  chloride  multiplied  by  0.25424 
gives  the  hydrochloric  acid  in  the  volume  taken. 

Instead  of  2/5  normal  caustic  soda  the  corresponding  2/5  normal 
caustic  potash  may  be  used.  To  prepare,  substitute  220  grams 
of  KOH  for  175  grams  of  NaOH,  and  proceed  as  directed  in  the 
scheme. 

The  standard  hydrochloric  acid  used  in  the  determination  itself 
is  not  exactly  2/5  normal;. in  fact,  is  much  weaker  than  this.  It 
is  made  so  in  order  to  avoid  waste  of  the  alkali.  If  made  -/5  nor- 
mal strength,  it  would  require  about  12.5  cc.  of  alkali  to  titrate 
back.  A  smaller  pipette  might  be  used  or  the  acid  measured  with 
a  burette.  The  automatic  pipettes  are  usually  made  in  sizes,  25  cc., 
50  cc.,  etc.,  and  are  so  convenient  for  measuring  the  acid  that, 
.as  there  is  nothing  to  be  gained  by  making  the  acid  2/5  normal 
strength,  it  will  be  found  more  convenient  to  make  it  of  the 
strength  indicated  in  the  scheme,  and  use  a  50  cc.  automatic 
pipette. 

In  some  laboratories,  the  acid  and  alkali  are  both  made  of  1/-(  N 
strength  and  a  half  gram  sample  is  used  for  the  determination. 
There  appears  to  be  nothing  gained  by  this  and  something  may  be 
lost  as  the  stronger  acid  is  a  better  solvent  for  the  sample. 

The  bottle  of  strong  hydrochloric  acid,  used  to  make  the  stand- 
ard acid,  should  be  marked  with  the  number  of  cubic  centimeters 
required  to  make  eight  liters  of  standard  acid  and  put  away  for 
use  in  making  up  the  next  lot  of  acid. 

In  preparing  a  second  lot  of  acid  it  will  save  calculation  and  the 
preparation  of  a  new  table,  if  the  acid  is  made  up  to  the  same 


ANALYTICAL  METHODS 


241 


strength  as  before.  To  do  this  make  a  little  weaker  than  the  fig- 
ures call  for  and  ascertain  its  strength  by  a  trial  determination 
on  the  standard  sample,  then,  if  too  much  carbonate  of  lime  is 
found,  add  acid  cautiously  until  the  value  of  a  determination  made 
with  the  standard  sample  shows  the  proper  percentage  of  lime. 

Standard  nitric  acid  may  be  used  in  place  of  the  standard  hy- 
drochloric acid.  It  keeps  better  and  is  not  quite  so  volatile,  but, 
on  the  other  hand,  is  not  so  good  a  solvent.  On  the  cement  rock 
mixtures  of  the  Lehigh  District  hydrochloric  acid  works  best,  but 


Fig.  62,  Standard  for  Acid  and  Alkali  Bottles  and  Pipettes 

nitric  acid  is  used  in  the  laboratories  of  several  of  the  wet  process 
mills  in  the  west.  The  nitric  acid  is  prepared  exactly  as  the  hy- 
drochloric acid,  using  such  a  quantity  of  strong  acid,  however, 
as  will  contain  167  grams  of  HNCX. 


242 


PORTLAND   CEMENT 


The  object  of  the  long  glass  tube  is  that  of  a  condenser  to  catch 
any  volatilized  acid.  This  may  be  replaced  by  a  Leibig's  return 
condenser  cooled  by  water  or  by  a  tube  full  of  glass  beads,  which 
are  wet  before  the  determination  with  cold  distilled  water. 

Fig.  62  shows  a  convenient  way  of  arranging  the  bottles,  bu- 
rettes and  pipette  for  the  acid  and  alkali.  Its  construction  is  so 
evident  from  the  drawing  that  a  description  seems  unnecessary. 
Both  the  burette  and  pipette  are  of  the  Eimer  and  Amend  auto- 
matic zero  point  pattern.  Fig.  63  shows  the  pipette  in  detail. 


Fig.  63,  Automatic  Pipette. 

A  perpetual  table  for  use  with  any  strength  acid  and  alkali  may 
be  made  as  follows :  The  number  of  cubic  centimeters  and  twen- 
tieths cubic  centimeter  of  alkali  from  3  to  8  are  written  on  a 
piece  of  stiff  paper  and  pasted  fast  to  a  soft  pine  board.  The  per- 
centages and  tenths  of  carbonate  of  lime  from  70  to  78  are  next 
written  on  a  piece  of  cardboard  and  this  is  merely  fastened  to  the 
board  with  thumb  tacks  so  that  the  number  of  cubic  centimeters 
of  acid  required  by  the  standard  sample  coincide  with  the  percent- 


ANALYTICAL  METHODS 


age  of  lime  it  contains.  For  instance,  in  the  example  given  75 
per  cent,  lime  are  made  to  coincide  with  4.6  cc.  of  alkali.  The 
board  is  then  to  be  hung  up  on  the  wall  behind  the  alkali  burette, 
etc. 

By  Scheibler's  Calcimeten 

Apparatus. 

Fig.  64  shows  the  form  of  the  calcimeter.  It  consists  of  the 
following  parts: 

i.  A  small  bottle,  A,  provided  with  a  perforated  stopper.  In 
the  bottle  is  placed  a  tube,  s,  of  gutta-percha  or  glass. 


Fig.  64,  Scheibler's  Calcimeter. 

2.  Another  bottle,  B,  provided  with  three  openings  in  its  neck. 
The  right  hand  opening  of  the  bottle  contains  a  firmly  fixed  glass 
tube  which  connects,  on  the  one  end  with  A  by  means  of  the  flex- 
ible rubber  tube,  r,  and  on  the  other,  inside  of  the  bottle,  B,  with 
a  very  thin  India-rubber  bladder,  K.  The  left  hand  opening  is 


244  PORTLAND  CEMENT 

controlled  by  a  pinch-cock  on  a  piece  of  rubber  tubing  slipped 
over  the  glass  tube,  q.  The  central  opening  connects  B  with  the 
measuring  tube. 

3.  An  accurately  graduated  glass  cylinder,  C,  of  about  150  cc. 
capacity. 

4.  Another  glass  cylinder,  D,  serving  to  regulate  the  pressure 
of  the  gas  measured  in  C. 

5.  A  water  reservoir,  E,  consisting  of  a  two-necked  Woulff 
bottle.    A  glass  tube,,  p,  passes  through  a  stopper  in  one  neck  near- 
ly to  the  bottom  of  the  reservoir  and  is  connected  with  D  by  means 
of  a  piece  of  rubber  tubing.     The  communication  between  D  and 
E  is  controlled  by  means  of  a  spring  clamp. 

The  whole  apparatus  with  the  exception  of  the  first  bottle,  A, 
is  fastened  to  a  suitable  stand  by  means  of  brass  fittings  and  a 
thermometer  is  also  attached. 

Open  the  spring  clamp,  p}  and  pour  distilled  water  into  D  by 
means  of  a  funnel  until  the  bottle,  E,  is  nearly  full.  When  ready 
for  a  determination,  remove  the  stopper  from  A,  open  the  spring 
clamp,  p,  and  blow  air  into  v  from  the  mouth  until  the  level  of  the 
water  in  C  and  D  reaches  the  zero  point  in  the  former.  Care 
should  be  taken  not  to  blow  the  water  into  the  tube,  u.  If  the 
level  of  the  water  passes  the  zero  mark  on  C,  it  may  be  brought  to 
the  proper  point  by  opening  the  spring  clamp,  p.  The  level  in 
both  tubes  should  be  the  same  and  stand  exactly  at  the  zero  mark 
in  C.  The  filling  of  the  tube,  C,  will  cause  the  bladder,  K,  to 
empty.  If  this  does  not  happen,  open  the  clamp,  q,  and  blow  air 
into  B  until  the  bladder  flattens.  If  K  is  exhausted  before  C  is 
filled  the  water  in  this  latter  tube  will  stand  below  that  in  D ;  in 
this  case  also  open  q  until  the  levels  are  the  same  and  at  the  zero 
point  in  C. 

The  Determination. 

Place  in  the  bottle,  A,  a  weighed  quantity  of  the  dried  slurry, 
cement  mixture  or  limestone,  in  a  finely  powdered  condition.  Fill 
the  cup,  s,  with  10  cc.  of  dilute  (i  :  i)  hydrochloric  acid  and  place 
cautiously  in  A  taking  care  not  to  spill  any  of  the  acid  into  the 
bottle.  Stopper  A  tightly,  greasing  the  glass  stopper  with  a  little 
tallow.  This  will  cause  the  water  in  C  to  sink  and  in  D  to  rise 


ANALYTICAL,  METHODS  245 

a  little.  Open  q  until  the  levels  are  the  same,  close  and  note  the 
thermometer  and  barometer  reading.  Raise  the  bottle  and  tilt  it 
slightly  so  that  the  acid  in  j  runs  into  A,  and  gradually  mixes  with 
the  sample.  In  doing  this  hold  the  bottle  by  the  neck,  to  avoid 
warming,  with  the  right  hand  and  at  the  same  time  regulate  p 
with  the  left  so  that  the  water  in  the  two  tubes  is  kept  at  the  same 
height.  Continue  this  operation  until  the  water  in  C  does  not 
change  its  level  for  a  few  seconds.  Now  bring  the  columns  of 
water  in  C  and  D  to  the  same  level  and  take  the  height  in  the 
tube,  C,  and  note  the  reading  of  the  thermometer  to  see  if  the  tem- 
perature has  remained  constant. 

Calculation  of  Results. 

It  is  necessary  as  the  first  step  to  calculating  the  weight 
of  calcium  oxide  equivalent  to  the  volume  of  gas  gives  off, 
to  correct  such  volume  for  temperature,  pressure,  the  ten- 
sion of  aqueous  vapor  and  the  gas  absorbed  or  held  back  by 
the  hydrochloric  acid.  This  latter  amounts  to  7  per  cent,  of  the 
volume  given  off.1  To  make  the  necessary  corrections  use  the 
formula 


93         \i  +0.00367  /         76 
in  which 

V  =  corrected  volume  (in  cc) 
v  —  uncorrected  volume  (in  cc.  ) 
t  =  temperature,  C° 
p  =  pressure,  mm.  of  mercury 

^  =  tension  of  aqueous  vapor  at  /°  C.  as  given  in  the  table  on 
page  98. 

To  find  the  weight  of  V  cc.  of  carbon  dioxide,  multiply  V  by 
0.0019712,  the  weight  of  I  cc.  of  carbon  dioxide,  when  measured 
at  o°  C.  and  760  mm.  of  mercury  pressure.  To  convert  this 
weight  of  carbon  dioxide  to  its  equivalent  of  lime,  CaO,  multi- 
ply this  latter  result  by  1.2743  ;  or  to  convert  to  calcium  carbonate, 
CaCCX,  multiply  by  2,2743. 


Or  :  Weight  of  CaO  =  0.002689  X  v  (- 


-j-  00467  t         760 

1  Warrington,  Chemical  News,  XXXI.,  253. 


246 


PORTLAND  CEMENT 


TABLE  XXIII. — TENSION  OF  AQUEOUS  VAPOR. 


/. 

Temp.  °C. 

j. 

Tension  in 
mm.  of 
mercury. 

i. 

Temp.  °C. 

J. 
Tension  in 
mm  of 
mercury. 

t. 
Temp.  °C. 

s. 
Tension  in 
mm.  of 
mercury. 

IO 

9.2 

18 

15-4 

26 

25.0 

II 

9.8 

19 

16.3 

27 

26.5 

12 

10.5 

20 

17.4 

28 

28.! 

13 

II.  2 

21 

I8.5 

29 

29.8 

14 

ii.  9 

22 

19.7 

30 

31-6 

15 

12.7 

23 

20.9 

31 

33-4 

16 

13.5 

24 

22.2 

32 

35-4 

17 

14.4 

25 

23-5 

33 

37-4 

Notes. 

Tables  are  usually  sold  with  these  instruments  which  very  much 
shorten  the  calculations,  a  graphic  table  such  as  the  author  de- 
scribes in  his  "Chemists'  Pocket  Manual"  would  greatly  simplify 
the  calculations  necessary  with  this  instrument. 

The  above  corrections  for  the  volume  of  carbon  dioxide  may 
be  done  away  with,  by  making  a  determination  either  with  a 
standard  sample  of  slurry  or  cement  mixture  or  with  pure  cal- 
cium carbonate  (Iceland  spar)  before  each  series  of  experiments 
with  this  instrument.  If  the  temperature  and  pressure  remain 
the  same  during  the  time  for  the  series  the  result  with  the  stand- 
ard sample  will  give  the  relation  between  the  volume  of  carbon 
dioxide  and  the  weight  of  lime.  For  example,  0.5  gram  of  finely 
powdered  Iceland  spar  (CaCO3)was  weighed  out  and  the  volume 
of  carbon  dioxide  then  measured  and  found  to  be  111.5  cc-  °-7 
gram  of  the  slurry,  whose  percentage  of  lime  is  desired,  was  next 
weighed  out  and  the  volume  of  gas  found  to  be  116.5  cc-  Now 
0.5  gram  of  calcium  carbonate  is  equivalent  to  0.28  gram  of  lime. 
Then,  volume  of  gas  given  off  by  the  Iceland  spar :  that  given  off 
by  the  slurry : :  weight  of  lime  in  Iceland  spar :  that  in  the  slurry ; 
or  111.5:  116.5::  0.28:  x  from  which  ^  =  0.2927,  and  per  cent. 

0.2927  X  ioo 
of  lime  in  slurry  = • =  41.81. 


ANALYTICAL  METHODS  247 

The  apparatus  should  be  placed  where  direct  sunlight  cannot 
fall  upon  it,  and  also  be  protected  from  any  heating  apparatus, 
such  as  radiator  or  stove,  or  Bunsen  burner.  It  should  also  be 
stood  near  a  north  window  so  as  to  have  sufficient  light  for  read- 
ing and  adjusting  the  water  levels. 

The  Dietrich,  Faija  and  Marshall  calcimeters  are  all  improve- 
ments upon  the  Scheibler  apparatus.  The  latter  is  probably  the 
best  of  the  three  and  is  described  in  Butter's  Volumetric  Analysis, 
page  106  and  also  in  Jour.  Soc.  Chem.  Ind.,  1898,  p.  1106. 

By  Permanganate. 

Weigh  0.5  gram  of  the  sample  into  a  platinum  crucible  and  mix 
intimately,  by  stirring  with  a  glass  rod,  with  ^  gram  of  finely 
powdered  dry  solution  carbonate.  Brush  off  the  rod  into  the  cru- 
cible with  a  camel's-hair  brush.  Cover  the  crucible  and  place  over 
a  low  flame.  Gradually  raise  the  temperature  until  the  crucible  is 
red  hot.  Then  after  a  minute  or  two  remove  to  the  blast  lamp 
and  ignite  for  5  minutes.  Cool  the  crucible  by  plunging  its  bot- 
tom in  cold  water  and  place  in  a  400  cc.  beaker.  Cover  with  a 
watch  glass  and  add  40  cc.  of  (1-4)  hydrochloric  acid  (or  20  cc. 
of  water  and  20  cc.  of  hydrochloric  acid,  (i-i)  ).  Heat  on  a  hot 
plate  until  solution  is  complete.  Lift  out  the  crucible  with  a  glass 
rod,  bent  in  a  crook  at  one  end,  and  rinse  it  off  into  the  beaker. 
Heat  the  contents  of  the  beaker  to  boiling,  add  ammonia  until 
alkaline,  and  then  10  cc.  of  a  ten  per  cent,  solution  of  oxalic  acid, 
and  proceed  as  directed  on  page  189. 

This  method  will  be  found  very  useful  in  checking  the  acid  and 
alkali  determinations. 

DETERMINATION  OF  SILICATES 

In  order  to  better  control  the  mixture  of  raw  materials  it  is 
often  of  advantage  to  determine  the  insoluble  matter  or  silicates. 
This  practice  differs  considerably  at  different  works,  but  the  fol- 
lowing will  illustrate  the  general  run  of  methods. 

By  Solution  and  Precipitation* 

Weigh  0.5  gram  of  the  sample  into  a  porcelain  dish  or  casserole, 
add  10  cc.  of  dilute  (i-i)  hydrochloric  acid  and  a  few  drops  of 
nitric  acid,  and  evaporate  to  dryness,  as  rapidly  as  possible,  with- 


248  PORTLAND   CEMENT 

out  spattering.  Bake  at  about  120°  C.  until  all  odor  of  acid  has 
disappeared  from  the  contents  of  the  dish.  Cool  the  latter,  add 
10  cc.  of  dilute  (i-i)  hydrochloric  acid  and  cover  with  a  watch 
glass.  Heat  for  a  few  minutes  and  add  50  cc.  of  hot  water.  Boil 
a  few  minutes  and  add  ammonia  in  faint  excess.  Boil  a  little 
longer,  allow  to  settle  and  filter.  Wash  with  hot  water  a  few 
times,  ignite  and  wreigh.  The  residue  is  called  "the  silicates"  and 
should,  provided  the  mix  is  of  proper  composition,  bear  a  certain 
ratio  to  the  percentage  of  carbonate  of  lime.  This  ratio  varies  at 
different  mills,  but  the  figure  is  usually  around  3.6. 

By  Solution. 

Weigh  0.5  gram  of  the  mixture  into  a  beaker  and  boil  with  10 
per  cent,  hydrochloric  acid  for  five  minutes.  Filter  off  the  in- 
soluble matter,  wash,  ignite  and  weigh.  This  method  is  in  use  in 
the  laboratories  of  the  Sandusky  Portland  Cement  Co.,  and  the 
mix  is  so  proportioned  as  to  give  a  certain  ratio  between  this  "in- 
soluble matter"  and  the  lime.  This  ratio  varies  at  the  two  mills  of 
the  company.  At  the  Sandusky  mill  the  ratio  is  3.9  and  at  the 
Syracuse  mill  it  is  4.2,  the  higher  ratio  being  due  to  the  more 
silicious  clay  at  the  latter  point. 

COMPLETE    ANALYSIS    OF    CEMENT    MIXTURE    OR 

SLURRY. 

Method  of  the  Committee  on  Uniformity  in  Analysis  of  Materials 
for  the  Portland  Cement  Industry  of  the  New  York  Sec- 
tion of  the  Society  of  Chemical  Industry* 

One-half  gram  of  the  finely  powdered  substance  is  weighed  out 
and  strongly  ignited  for  15  minutes,  or  longer  if  the  blast  is  not 
powerful  enough  to  effect  complete  conversion  to  cement  in  this 
time.  It  is  then  transferred  to  an  evaporating  dish,  preferably  of 
platinum  for  the  sake  of  celerity  in  evaporation,  and  the  analysis 
completed  as  directed  on  page  170,  by  moistening  with  water  and 
digesting  with  hydrochloric  acid,  etc. 

The  above  method  is  tedious  and  so  cumbersome  and  long  as  to 
preclude  its  use  in  cement  mill  laboratories,  where  samples  of  the 
mix  are  analyzed  daily,  except  for  the  preparation  of  standard 
samples.  Even  these  should  be  analyzed  also  by  the  method  in 
daily  use  in  the  laboratory  in  order  to  get  all  the  work  on  the 


ANALYTICAL  METHODS  249 

same  relative  basis  and  the  longer  and  more  accurate  results 
should  only  be  used  to  check  the  shorter  mill  scheme,  and  to  make 
sure  that  the  results  of  the  latter  are  not  too  wide  of  the  truth. 
The  results  which  should  actually  be  used  as  the  values  for  the 
carbonate  of  lime,  etc.,  in  the  samples  should  be  those  obtained 
by  the  regular  mill  scheme.  If  this  is  not  done,  acid  and  alkali 
will  give  one  set  of  results  and  a  complete  analyses  another,  etc. 

The  scheme  given  below  is  modeled  after  those  generally  in 
use  in  cement  mill  laboratories  and  combines  a  fair  degree  of  ac- 
curacy with  rapidity  and  convenience  of  execution. 

Method  of  the  Committee  on  the  Analysis  of  Portland  Cement 

and  Cement  Materials  of  the  Lehigfh  Valley  Section  of  the 

American  Chemical  Society. 

Weigh  0.5  gram  of  the  finely  ground  sample  into  a  small  plati- 
num crucible  and  mix  intimately,  by  stirring  with  a  glass  rod, 
with  0.5  gram  of  pure  dry  finely  powdered  sodium  carbonate. 
Brush  off  the  rod  into  the  crucible  with  a  camel's-hair  brush. 
Cover  the  crucible  and  place  over  a  low  flame.  Gradually  raise 
the  latter,  until  the  crucible  is  red  hot,  and  continue  heating,  in 
the  full  flame  of  the  Bunsen  burner,  for  five  minutes  longer ;  then 
place  over  a  blast  lamp  and  heat  for  five  minutes  more.  Cool  and 
place  the  crucible  on  its  side  in  a  porcelain  casserole  or  dish,  or 
preferably  a  platinum  dish,  and  dissolve  the  mass  in  10  cc.  of 
water  and  10  cc.  of  hydrochloric  acid.  Heat  until  solution  is 
complete,  keeping  the  dish  covered  to  avoid  loss  by  effervescence. 
When  everything,  except  a  little  gelatinous  silica,  which  usually 
separates  out,  is  in  solution,  remove  the  crucible  and  clean  off 
into  the  dish  with  a  rubber-tipped  rod.  Evaporate  to  dryness  at 
a  moderate  heat,  continuing  to  heat  the  mass — not  above  200°  C. 
— until  all  odor  of  acid  is  gone.  Do  not  hurry  this  baking  or 
skimp  the  time.  The  whole  success  of  the  analysis  depends  on 
thoroughness  at  this  point.  Cool;  add  20  cc.  hydrochloric  acid 
(i-i)  ;  cover,  and  boil  gently  for  ten  minutes;  add  30  cc.  water, 
raise  to  boiling,  and  filter  off  the  silica ;  wash  with  hot  water  four 
or  five  times;  put  in  crucible,  ignite  (using  blast  for  10  minutes), 
and  weigh  as  SiO2. 


25O  PORTLAND  CEMENT 

Iron  and  Alumina. 

Make  filtrate  alkaline  with  ammonia,  taking  care  to  add  only 
slight  excess ;  add  a  few  drops  of  bromine  water  and  boil  till  odor 
of  ammonia  is  faint.  Filter  off  the  hydroxides  of  iron  and  alum- 
inum, washing  once  on  the  filter.  Dissolve  the  precipitate  with 
hot  dilute  nitric  acid,  reprecipitate  with  ammonia;  boil  five  min- 
utes ;  filter  and  wash  the  iron  and  alumina  with  hot  water  once ; 
place  in  crucible,  ignite  carefully,  using  blast  for  5  minutes,  and 
weigh  combined  iron  and  aluminum  oxides. 

Iron. 

If  it  is  desired  to  separate  the  two  oxides  add  four  grams  acid 
potassium  sulphate  to  the  crucible  and  fuse  at  a  very  low  heat 
until  oxides  are  wholly  dissolved — twenty  minutes  at  least;  cool; 
place  crucible  and  cover  in  small  beaker  with  50  cc.  water;  add 
15  cc.  dilute  sulphuric  acid  (1-4)  ;  cover  and  digest  at  nearly  boil- 
ing until  melt  is  dissolved;  remove  crucible  and  cover,  rinsing 
them  carefully.  Cool  the  solution  and  add  10  grams  powdered  C. 
P.  zinc,  No.  20.  Let  stand  one  hour,  decant  the  liquid  into  a 
larger  beaker,  washing  the  zinc  twice  by  decantation,  and  titrate 
at  once  with  permanganate.  Calculate  the  Fe2O3  and  determine 
the  A12O3  by  difference.  Test  Zn,  etc.,  by  a  blank  and  deduct.1 

Lime. 

Make  the  filtrate  from  the  hydroxides  alkaline  with  ammonia; 
boil ;  add  20  cc.  boiling  saturated  solution  ammonium  oxalate ; 
continue  boiling  for  five  minutes ;  let  settle  and  filter.  Wash  the 
calcium  oxalate  thoroughly  with  hot  water,  using  not  more  than 
125  cc.,  and  transfer  it  to  the  beaker  in  which  it  was  precipitated, 
spreading  the  paper  against  the  side  and  washing  down  the  pre- 
cipitate first  with  hot  water  and  then  with  dilute  sulphuric  acid 
(1-4);  remove  paper;  add  50  cc.  water,  10  cc.  Cone,  sulphuric 
acid,  heat  to  incipient  boiling  and  titrate  with  permanganate,  cal- 
culating the  CaO. 

1 1ron  may  also  be  determined  by  using  a  separate  sample,  igniting  with  half  its 
weight  sodium  carbonate,  dissolving  the  mass  in  hydrochlpric  acid  and  titrating  with 
stannous  chloride  as  directed  on  page  196,  or  the  iron  may  be  precipitated  with  ammonia 
redissolved  in  sulphuric  acid,  and  the  iron  determined  by  reduction  with  zinc  and  titra- 
tion  with  permanganate.  (See  page  190  ). 


ANALYTICAL  METHODS  25! 

Magnesia. 

If  the  filtrate  from  the  calcium  oxalate  exceeds  250  cc. ;  acidify, 
evaporate  to  that  volume;  cool,  and  when  cold  add  15  cc.  strong" 
ammonia  and  with  stirring  15  cc.  stock  solution  of  sodium  hy- 
drophosphate.  Allow  to  stand  in  the  cold  six  hours  or  preferably 
over  night ;  filter ;  wash  the  magnesium  phosphate  with  dilute  am- 
monia (1-4)  plus  100  gms.  ammonium  nitrate  per  liter;  put  in 
crucible,  ignite  at  low  heat  and  weigh  the  magnesium  pyrophos- 
phate. 

OTHER  CONSTITUENTS. 

For  the  determination  of  sulphur,  carbon  dioxide,  hygroscopic 
and  combined  water,  and  alkalies,  refer  to  the  methods  given 
under  cement.  The  fusion  method  is  to  be  used  for  determining 
sulphur,  which  is  usually  present  as  sulphide  (iron  pyrites)  or  in 
combination  with  organic  matter  in  mixtures  of  marl  and  clay. 
Calcium  sulphate  may  be  determined  by  simple  solution  in  hydro- 
chloric acid  as  in  cement. 


CHAPTER  XL 


THE  ANALYSIS  OF  THE  RAW  MATERIALS. 


SAMPLING. 
Limestone  and  Cement  Rock. 

Limestone  deposits  should  be  sampled  by  means  of  core  or 
churn  drills,  sinking  the  test  holes  to  a  considerable  depth.  Sur- 
face samples,  knocked  off  here  and  there,  are  of  no  value  and  the 
time  spent  in  analyzing  any  number  of  them  is,  in  most  cases, 
thrown  away.  In  sampling  limestone  or  other  solid  material,  the 
surface  dirt  and  clay  should  be  shoveled  away  and  the  weathered 
rock  removed.  The  drill  can  then  be  set  up  and  the  sample  taken. 
In  prospecting  a  limestone  property,  it  is  usual  to  make  a  map 
showing  the  topography,  etc.,  and  this  should  be  divided  into 
squares  having  sides  of  say  50  to  300  feet.  Drill  holes  can 
then  be  sunk  at  the  corners  of  each  square  and  the  cores  or  chips 
brought  up  by  the  drill  saved  for  analysis.  Usually  it  is  the  cus- 
tom, instead  of  making  one  sample  of  all  the  rock  brought  up  by 
the  drill  from  a  hole,  to  make  separate  samples  of  the  material 
brought  up  from  various  depths.  Thus  one  sample  would  repre- 
sent the  material  brought  up  from  a  depth  of  hole  from  o  to  10 
feet,  while  the  next  would  represent  that  taken  by  the  drill  in 
going  from  10  to  20  feet,  etc.  By  doing  this,  the  uniformity  of 
the  deposit,  as  well  as  its  freedom  from  bands  of  magnesium 
stone,  etc.,  can  be  tested. 

After  the  analyses  are  all  made,  charts  or  plots  should  be 
drawn  showing  the  amount  of  stripping  to  be  done  (dirt  to  be  re- 
moved), the  quality  of  the  rock  at  various  depths  and,  if  the  drill- 
ing is  carried  far  enough,  the  depth  of  the  deposit  at  each  point. 
This  can  be  shown  easiest  by  means  of  sections,  cutting  the  depos- 
it, along  the  line  of  squares,  drawn  to  scale  and  showing,  by 
means  of  various  kinds  of  shading,  the  stripping,  etc.  From  these 
charts  the  amount  of  rock  available  and  the  earth  which  must  be 
removed  to  get  at  this  can  be  calculated.  In  many  quarries  the 


ANALYTICAL  METHODS  .  253 

material  removed  by  the  drill,  in  preparing  for  a  blast,  is  used  as 
a  sample  in  order  to  give  the  chemist  the  data  for  making  the 
mixture  of  limestone  and  clay. 

The  churn  drill  is  made  by  the  Ingersoll-Rand  Drill  Co.,  the 
Keystone  Driller  Co.,  and  others,  and  consists  of  a  cylinder  mounted 
on  a  heavy  tripod  and  provided  with  a  piston  to  which  is  attached 
the  drill  rod.  The  cutting  edge  of  the  latter  is  usually  in  the  form 
of  an  X  and  each  cutting  edge  is  about  4  inches  long.  Either  air 
or  steam  can  be  used  to  operate  the  drill,  though  the  latter  is  al- 
most always  used  in  prospecting,  as  a  small  portable  boiler  is  all 
that  is  needed  to  supply  this.  The  drilling  of  test  holes  should  al- 
ways be  in  the  hands  of  an  experienced  driller. 

The  chips  or  mud  from  the  churn  drill  should  be  dried,  if  nec- 
essary, and  sent  to  the  laboratory  in  clean  bags  of  cloth  or  paper, 
or  in  round  tin  boxes,  etc.  There  the  sample  should  be  crushed 
and  quartered  down  to  laboratory  dimensions — the  final  sample 
being  made  to  pass  a  2OO-mesh  sieve. 

Core  drills  are  also  much  used  in  prospecting  limestone.  These 
cut  a  round  cylinder  or  core  of  rock,  2  or  3  inches  in  diameter,  as 
they  pass  into  the  rock.  For  some  purposes  these  cores  are  very 
valuable,  as  they  allow  an  inspection  of  the  sample  as  to  stratifi- 
cation, etc.,  and  any  thin  bands  of  quartz,  etc.,  are  shown  at  once. 
The  drills  themselves  are  expensive,  however,  and  troublesome  to 
operate  and  repair,  as  the  cutting  is  done  by  means  of  diamonds 
set  in  the  end  of  the  drill.  Recently  the  Davis-Calyx  Drill  Co., 
has  brought  out  a  core  drill  which  works  on  a  different  principle 
and  which  has  given  excellent  satisfaction. 

Clay  and  Shale. 

Clay  can  be  sampled  in  a  number  of  ways,  such  as  by  digging 
pits  or  sinking  test  holes  by  means  of  an  auger  drill  or  a  serrated 
pipe.  Hard  clays  and  shales  will  require  either  the  auger  or 
churn  drill.  The  churn  drill  has  been  described  in  the  preceding 
section,  and  the  auger  drill,  for  use  in  sampling,  is  similar  to  those 
vised  for  coal  cutting,  etc.  The  serrated  pipe  consists  of  a  pipe, 
the  end  of  which  has  been  filed  and  tempered  to  form  sharp  teeth 
like  a  saw.  This  is  forced  down  into  the  clay  by  twisting  a  handle 
at  the  upper  end.  The  result,  when  withdrawn,  is  a  plug  of  clay, 


254  PORTLAND  CEMENT 

filling  the  pipe  and  representing  the  strata  through  which  the  lat- 
ter has  passed. 

Clay  deposits  should  be  mapped  out  carefully,  as  different  parts 
of  the  bed  may  show  very  different  proportions  of  silica  and 
alumina,  and  in  order  to  get  a  cement  with  uniform  setting  prop- 
erties it  may  be  necessary  to  work  two  or  more  parts  of  the  de- 
posit in  conjunction,  in  order  to  keep  the  ratio  between  the  silica 
and  alumina  constant. 

The  depth  of  the  deposit  should  also  be  determined  so  that  a 
calculation  of  the  available  quantity  of  clay  may  be  made. 

Marl. 

For  sampling  marl,  a  tube,  similar  to  that  used  for  sampling 
cement,  may  be  employed  to  advantage.  This  is  described  on 
page  1 68,  or  the  serrated  pipe  described  before  may  be  used.  If 
the  marl  deposit  is  very  wet,  a  long  pipe  having  a  plug  at  one  end 
may  be  used.  This  plug  should  be  of  iron,  have  a  sharp  point,  fit 
the  mouth  of  the  pipe  closely  and  be  fastened  to  a  long  thin  iron 
rod.  In  using  the  sampler,  the  iron  plug  is  drawn  up  against  the 
mouth  of  the  pipe  and  the  latter  is  thus  shoved  down  to  the  depth 
at  which  the  sample  is  to  be  taken.  The  pipe  is  then  raised  and 
shoved  down  to  its  former  level,  being  forced  tight  against  the 
iron  plug.  The  pipe  is  then  raised  by  means  of  the  rod  and  the 
sample  dumped  out. 

An  excellent  sampler  can  also  be  made  from  two  pieces  of  brass 
pipe  similar  to  the  grain  sampler  described  on  page  169. 

Marl  deposits  should  be  very  thoroughly  mapped  out,  not  only 
as  to  quality,  but  also  as  to  the  depth  of  the  deposit  in  order  that 
the  quantity  available  for  manufacturing  purposes  may  be  calcu- 
lated, since  the  value  of  marl  deposits  depends  in  most  cases  as 
much  upon  quantity  as  quality. 

METHODS    FOR   LIMESTONE,    CEMENT-ROCK    AND 

MARL. 

By  Ignition  of  the  Sample  with  Sodium  Carbonate* 

Silica. 

Weigh  0.5  gram  of  finely  ground  dried  sample  into  a  platinum 
crucible  and  mix  intimately  with  0.5  gram  of  pure  dry  sodium 


ANALYTICAL,  METHODS  255 

carbonate  by  stirring  with  a  glass  rod.  Place  the  crucible  over 
a  low  flame  and  gradually  raise  this  latter  until  the  crucible  is  red 
hot.  Continue  heating  for  five  minutes,  then  substitute  a  blast 
lamp  for  the  Bunsen  burner  and  heat  for  five  minutes  longer. 
Place  the  crucible  in  a  dish  or  casserole,  add  40  cc.  of  water  and 
10  cc.  of  hydrochloric  acid,  and  digest  until  all  the  mass  is  dis- 
solved out  of  the  crucible.  Clean  off  the  crucible  inside  and  out- 
side, add  a  few  drops  of  nitric  acid  to  the  solution  and  evaporate 
it  to  dryness.  Heat  the  residue  at  110°  C.  for  one  hour,  cool,  add 
15  cc.  of  dilute  hydrochloric  acid,  cover  with  a  watch  glass  and 
digest  for  a  few  minutes  on  the  hot  plate.  Dilute  with  50  cc.  of 
hot  water,  heat  nearly  to  boiling,  and  filter.  Wash  the  residue 
well  with  hot  water.  Dry,  ignite,  and  weigh  as  silica,  SiO2. 

If  the  limestone  is  high  in  silica  a  trace  will  be  found  in  the  fil- 
trate from  the  silica  as  precipitated  above.  If  great  accuracy  is 
desired,  after  evaporation  to  dryness,  dissolve  the  mass  in  the 
dish  in  hydrochloric  acid  and  water  as  usual  without  heating  it  to 
110°  C.  for  one  hour  and  filter  and  wash.  Kvaporate  the  filtrate 
to  dryness,  and  again  dissolve  in  water  and  hydrochloric  acid,  fil- 
ter, and  wash.  Ignite  the  two  precipitates  together  and  weigh  as 
SiO2. 

Ferric  Oxide  and  Alumina. 

Heat  the  filtrate  to  boiling,  add  ammonia  in  slight  but  distinct 
excess,  boil  for  five  minutes  and  filter.  Wash  the  precipitate  twice 
with  hot  water.  Remove  the  filtrate  from  under  the  funnel  and 
in  its  place  stand  the  beaker  in  which  the  precipitation  was  made. 
Dissolve  the  precipitate  in  dilute  nitric  acid  and  wash  the  filter- 
paper  free  from  iron  with  cold  water.  Heat  the  solution  to  boil- 
ing and  precipitate  the  iron  and  alumina  with  ammonia  as  before. 
Filter,  allowing  the  filtrate  to  run  into  that  from  the  first  precipita- 
tion, wash  once  with  hot  water,  dry  and  ignite.  Weigh  and  re- 
port as  ferric  oxide  and  alumina. 

If  the  percentage  of  ferric  oxide  and  alumina  are  desired  sepa- 
rately, proceed  as  directed  in  A,  B,  or  C. 

A.  Fuse  the  precipitate  of  ferric  oxide  and  alumina,  after 
weighing,  with  a  little  sodium  carbonate,  dissolve  in  a  little  water 
to  which  a  few  cubic  centimeters  of  hydrochloric  acid  have  been 


256  PORTLAND   CEMENT 

added,  and  drop  into  the  solution  a  few  small  crystals  of  citric 
acid.  Add  ammonia  until  the  solution  smells  slightly  of  the  re- 
agent, and  then  an  excess  of  ammonium  sulphide.  Allow  the 
black  precipitate  to  settle,  filter,  wash  a  few  times,  dissolve  in  hy- 
drochloric acid,  add  a  little  bromine  water,  boil  a  while  and  add 
ammonia  in  slight  but  distinct  excess.  Filter,  wash  well  with  hot 
water,  ignite  and  weigh  as  Fe2O3.  Deduct  this  weight  from  that 
of  the  total  ferric  oxide  and  alumina,  for  the  weight  of  alumina, 
A1203.^ 

B.  Fuse   the   precipitate   of   ferric   oxide   and   alumina,   after 
weighing,  with  caustic  potash  in  a  silver  crucible  or  dish.     Treat 
the  fusion  with  water,  boil,  filter,  and  wash.     Dry,  ignite,  and 
weigh  the  residue  as  ferric  oxide,  Fe2O3.     Deduct  this  weight 
from  that  of  the  ferric  oxide  and  alumina,  for  the  weight  of  alum- 
ina, A12O3. 

C.  Dissolve  the  residue,  after  fusion  with  sodium  carbonate,  in 
a  little  dilute  hydrochloric  acid  and  determine  the  ferric  oxide 
volumetrically  by  the  method  given  on  page  196. 

Lime. 

Heat  the  filtrate  from  the  iron  and  alumina,  which  should  meas- 
ure between  300  and  500  cc.,  to  boiling  and  add  25  cc.  of  a  sat- 
urated solution  of  ammonium  oxalate.  Stir  and  boil  for  a  few 
minutes  and  allow  the  precipitate  one  hour  in  which  to  settle. 
Filter  and  wash  well  with  hot  water.  After  washing,  treat  the 
precipitate  as  directed  below  in  A  or  B. 

A.  Dry  the  precipitate  by  heating  over  a  low  flame,  in  a  weigh- 
ed platinum  crucible,  ignite  until  all  carbonaceous  matter  is  de- 
stroyed and  ignite  for  fifteen  minutes  over  a  blast  lamp.    Cool  and 
weigh.     Again  ignite   for  five   minutes   over   a  blast  lamp   and 
weigh.    If  this  weight  agrees  to  within  0.0002  gram  of  the  former 
one  it  may  be  taken  as  the  weight  of  the  calcium  oxide,  CaO.     If 
it  does  not  agree,  ignite  again  and  repeat,  if  necessary,  until  the 
weight  is  constant. 

B.  Punch  a  hole  in  the  filter  paper  and  wash  the  precipitate  into 
the  beaker  in  which  the  precipitation  was   formed.     Wash  the 
paper  with  dilute  sulphuric  acid  from  a  wash  bottle  and  then  with 
hot  water.     Dilute  the  solution  to  300  or  40  cc.,  heat  to  60°  or 


ANALYTICAL  METHODS  257 

70°  C.,  and  after  adding  10  cc.  of  dilute  sulphuric  acid  titrate  with 
permanganate.  Calculate  the  per  cent,  of  lime,  CaO,  or  calcium 
carbonate,  CaCCX,  in  the  limestone,  as  directed  under  ''Volu- 
metric Determination  of  Calcium,"  page  185. 

Magnesia. 

To  the  filtrate  from  the  calcium  oxalate  add  sufficient  hydro- 
chloric acid  to  make  it  slightly  acid,  and  30  cc.  of  sodium  phos- 
phate solution.  Concentrate  to  about  300  cc.  by  evaporation.  Set 
the  solution  in  a  vessel  of  cold  water  and  when  cooled  to  the  tem- 
perature of  the  latter  add  ammonia,  drop  by  drop,  from  a  burette, 
with  constant  stirring  until  slightly  ammoniacal  and  the  precipi- 
tate begins  to  form.  Stop  adding  ammonia  and  stir  for  five  min- 
utes, add  one-tenth  the  volume  of  the  liquid  of  strong  ammonia; 
and  continue  the  stirring  for  three  minutes  more.  Allow  the  solu- 
tion to  stand  in  a  cool  place  over  night,  filter,  wash  well  with  a 
mixture  of  1000  cc.  water,  500  cc.  ammonia  (sp.  gr.  0.96),  and 
150  grams  ammonium  nitrate.  Dry,  ignite,  and  weigh  as  mag- 
nesium pyrophosphate,  Mg2P2O7.  Multiply  this  by  0.36190  for 
its  equivalent  of  magnesia,  MgO,  or  by  0.75722  for  magnesium 
carbonate,  MgCO3. 

By  Solution  in  Hydrochloric  Acid* 

Insoluble  Silicious  Matter. 

Weigh  0.5  gram  of  the  finely  ground  dried  sample  into  a  porce- 
lain dish  or  casserole,  cover  with  a  watch  glass  and  add  30  cc. 
of  water  and  10  cc.  of  concentrated  hydrochloric  acid.  Warm 
until  all  effervescence  has  ceased,  uncover,  add  a  few  drops  of  ni- 
tric acid,  and  evaporate  to  dryness.  Bake  on  the  hot  plate  or 
sand-bath  until  all  odor  of  hydrochloric  acid  has  disappeared,  or 
safer  still,  heat  in  an  air  bath  at  110°  C.  for  one  hour  after  the 
residue  has  become  perfectly  dry.  Cool  the  dish  and  add  5  cc. 
of  dilute  hydrochloric  acid,  set  on  the  hot  plate,  covered  with  a 
watch  glass  for  five  minutes,  then  add  50  cc.  of  hot  water  and 
filter,  after  digesting  until  all  except  silicious  matter  dissolves. 
Wash  thoroughly,  ignite  and  weigh  as  "insoluble  silicious  mat- 
ter." 


258  PORTLAND  CEMENT 

Silica. 

Should  it  be  desirous  to  know  the  silica  in  the  "insoluble  sili- 
cious  matter"  fuse  it  with  ten  times  its  weight  of  pure  dry  sodium 
carbonate,  first  over  a  Bunsen  burner  turned  low,  and  then,  after 
slowly  raising  the  flame  of  this  latter  to  its  full  height,  over  a 
blast  lamp  until  the  contents  of  the  crucible  are  in  a  state  of  quiet 
fusion.  Remove  the  crucible  from  the  lamp  and  run  the  fused 
mass  well  up  on  its  sides  by  tilting  and  revolving  the  crucible 
while  held  with  the  crucible  tongs.  While  still  hot  dip  the  cruci- 
ble three-quarters  of  the  way  up  in  a  pan  of  cold  water  which 
will  frequently  cause  the  mass  to  loosen  from  the  crucible.  Wash 
off  any  material  spattered  on  the  crucible  cover  into  a  casserole 
or  dish  with  hot  water,  and  add  the  mass  in  the  crucible  if  it  has 
become  detached.  If  not,  fill  the  crucible  with  hot  water  and  set 
on  the  hot  plate  until  the  fused  mass  softens  and  can  be  removed 
to  the  casserole.  Dissolve  any  particles  of  the  mass  in  hydro- 
chloric acid,  that  adhere  too  firmly  to  the  crucible  to  be  removed 
by  gentle  rubbing  with  a  rubber-tipped  rod.  When  the  hot  water 
has  thoroughly  disintegrated  the  fused  mass,  cover  the  casserole 
or  dish  with  a  watch  glass  and  strongly  acidify  the  contents  with 
hydrochloric  acid.  Heat  until  all  effervescence  ceases  and  every- 
thing dissolves  except  the  silica.  Wash  off  the  watch  glass  into 
the  dish  and  evaporate  the  solution  to  dryness.  Heat  for  one  hour 
at  110°  C.  in  an  air-bath,  or  on  the  hot  plate  at  not  too  high  a  tem- 
perature until  all  odor  of  hydrochloric  acid  has  disappeared  from 
the  dry  mass.  Cool,  add  10  cc.  of  hydrochloric  acid  and  50  cc.  of 
water,  warm  until  all  soluble  salts  are  in  solution,  filter,  wash  well 
with  hot  water,  dry,  ignite,  and  weigh  as  silica,  SiO2. 
Fe2Oz,Al2Oz,CaO,MgO. 

Mix  the  two  filtrates  from  the  silica  separations  and  proceed  to 
determine  iron  and  alumina,  lime  and  magnesia,  as  directed  in  the 
method  "By  Ignition  with  Sodium  Carbonate." 

When  the  amount  of  sodium  carbonate  added  to  the  "insoluble 
silicious  matter"  is  greater  than  0.5  gram,  it  is  best  in  very  accu- 
rate work,  instead  of  mixing  the  two  filtrates  from  the  silica,  to 
determine  the  iron,  alumina,  lime,  and  magnesia  in  each  solution 
separately,  since  the  large  lime  precipitate  is  almost  sure  to  be  con- 
taminated with  sodium  salts  if  the  two  filtrates  are  mixed. 


ANALYTICAL  METHODS  259 

Determination  of  Organic  Matter,  Insoluble  Silicious  Matter,  Fer- 
ric Oxide  and  Alumina,  Lime  and  Magnesia. 

Weigh  i  gram  of  the  finely  ground  dried  limestone  into  a  porce- 
lain dish  or  casserole ;  cover  with  a  watch  glass  and  add  30  cc.  of 
water  and  10  cc.  of  concentrated  hydrochloric  acid.  Warm  until 
all  effervescence  ceases,  uncover  and  evaporate  to  dryness  on  a 
water  bath.  Heat  the  dish  for  one  hour,  after  the  residue  be- 
comes thoroughly  dry,  at  110°  C.  in  an  air-bath.  Cool  the  dish 
and  add  5  cc.  of  hydrochloric  acid  and  50  cc.  of  hot  water.  Heat 
until  all  soluble  salts  dissolve,  filter  upon  a  Gooch  crucible  or  a 
small  counterpoised  filter  paper.  WTash  well  with  hot  water,  dry 
at  100°  C.  in  an  air-bath  and  weigh  as  "organic  matter"  plus  "in- 
soluble silicious  matter." 

Now  ignite  until  all  carbonaceous  matter  is  destroyed,  and  cool 
and  weigh  as  "insoluble  silicious  matter."  This  weight  subtract- 
ed from  the  preceding  one  gives  the  "organic  matter."  If  the 
silica  in  the  "insoluble  silicious  matter"  is  desired,  fuse  the  latter 
with  ten  times  its  weight  of  sodium  carbonate  and  proceed  as  de- 
scribed in  the  preceding  scheme  for  the  analysis  of  limestone  "By 
Solution  in  Hydrochloric  Acid." 

Heat  the  filtrate  from  the  "organic  matter"  and  the  "insoluble 
silicious  matter"  to  boiling,  add  ammonia  in  slight  but  distinct  ex- 
cess, and  proceed  to  determine  the  ferric  oxide  and  alumina,  lime 
and  magnesia,  as  directed  on  page  255. 

The  Determination  of  Alkalies,  Sulphuric  Acid,  Carbon  Dioxide, 
Combined  Water  and  Loss  on  Ignition. 

For  the  determination  of  these  constituents  refer  to  the  meth- 
ods given  under  cement. 

Rapid  Determination  of  Lime  and  Magnesia. 

S.  B.  Newberry1  suggests  the  following  rapid  scheme  for  de- 
termining lime  and  magnesia  in  limestone,  etc.  "Prepare  one- 
fifth  normal  hydrochloric  acid  and  one-fifth  normal  caustic  soda 
solutions,  and  standardize  with  pure,  transparent  Iceland  spar. 
One-half  gram  of  spar  should  exactly  neutralize  50  cc.  of  acid. 

Weigh  out  one-half  gram  of  finely-ground  limestone,  transfer 
to  an  Erlenmeyer  flask  of  about  500  cc.  capacity,  provided  with 

1  Cement  and  Engineering  News,  March,  1903,  p.  35. 


260  PORTLAND   CEMENT 

rubber  stopper  and  thin  glass  tube  about  30  inches  long  to  serve  as 
a  condenser,  as  described  on  page  236.  Run  into  the  flask  60  cc. 
one-fifth  normal  acid;  attach  the  condenser  and  boil  gently,  al- 
lowing no  steam  to  escape  from  the  tube,  for  about  two  minutes. 
Wash  down  the  tube  into  the  flask  with  a  few  cc.  of  water  from 
wash-bottle;  remove  the  condenser  and  cool  the  solution  thor- 
oughly by  immersing  the  bottom  of  the  flask  in  cold  water.  When 
quite  cold,  add  five  drops  of  phenolphthalein  solution,  (i  gm.  in 
200  cc.  alcohol),  and  titrate  back  to  first  pink  color  with  one-fifth 
normal  soda  solution.  It  is  important  to  recognize  the  point  at 
which  a  faint  pink  color  first  appears  throughout  the  solution, 
even  though  this  may  fade  out  in  a  few  seconds.  If  alkali  be  add- 
ed to  a  permanent  and  strong  red  color,  the  lime  will  come  too 
low.  Let  us  call  the  amount  of  acid  used  the  first  acid,  and  the 
alkali  used  to  titrate  back  the  first  alkali. 

"Transfer  the  neutral  solution  to  a  large  test  tube,  twelve 
inches  long  and  one  inch  inside  diameter,  marked  (with  a  paper 
strip  or  otherwise)  at  100  cc.  Heat  to  boiling,  and  add  one-fifth 
normal  soda  solution,  about  one  cc.  at  a  time,  boiling  for  a  mo- 
ment after  each  addition,  till  a  deep  red  color,  which  does  not  be- 
come paler  on  boiling,  is  obtained.  This  point  can  be  easily  rec- 
ognized within  one-half  cc.  after  a  little  practice.  Note* the  no.  of 
cc.  soda  solution  added  to  the  neutral  solution,  as  second  alkali. 
Dilute  to  100  cc.,  boil  for  a  moment,  and  set  the  tube  aside  to  al- 
low the  precipitate  to  settle.  When  settled,  take  out  50  cc.  of  the 
clear  solution  by  means  of  a  pipette,  and  titrate  back  to  colorless 
with  one-fifth  normal  acid.  Multiply  by  2  the  no.  of  cc.  acid  re- 
quired to  neutralize,  and  note  as  second  acid. 

"The  calculation  is  as  follows: 

Second  alkali  —  second  acid,  X  2  X  0.40  =  %  MgO. 

First  acid — (first  alkali  -f-  second  alkali  —  second  acid), 
X  2  X  0.56  =  %  CaO. 

"Example :  To  one-half  gram  limestone  were  added  60.00  cc. 
acid,  (first  acid}.  To  titrate  back  to  first  pink,  11.60  cc.  alkali 
were  required,  (first  alkali).  The  solution  was  then  transferred 
to  test  tube,  boiled,  and  3.55  cc.  alkali  added  to  permanent  deep 
red  color,  (second  alkali).  After  diluting  to  100  cc.  and  settling, 


ANALYTICAL  MKTHODS  26l 

50  cc.  of  the  red  solution  required  0.45  cc.  acid  to  decolorize  it, 
(0.45  X  2  =  0.90  =  second  acid). 

3-55  —  0.90,  X  2X  0.40  =  2.12  %  MgO. 

60.00—  (n. 60  +  3.55  —  0.90)  X  2  X  0.56  =  51.24%  CaO. 

NOTES. 

"Nitric  acid  may  be  used  in  place  of  hydrochloric;  the  latter 
appears,  however,  to  give  slightly  better  results. 

"Not  more  than  I  c.c.  excess  of  alkali  should  be  added  in  pre- 
cipating  the  magnesia;  the  "second"  should  therefore  not  exceed 
i.o.  Larger  excess  of  alkali  tends  to  throw  down  lime. 

"The  settling  usually  requires  only  a  few  minutes,  unless  much 
magnesia  is  present ;  it  may  be  greatly  hastenend  by  allowing  the 
test-tube  to  stand  two  or  three  minutes,  then  immersing  the  lower 
part  for  a  moment  in  cold  water.. 

"If  results  are  desired  in  persentages  of  magnesium  carbonate 
and  calcium  carbonate,  the  factors  0.84  and  i.oo  are  to  be  substi- 
tuted for  0.40  and  0.56,  respectively. 

"The  tendency  of  the  method  is  to  give  slightly  too  high  results 
on  magnesia  and  too  low  results  on  lime.  This  is  partly  due  to  the 
formation  of  calcium  carbonate,  by  the  action  of  the  carbon 
dioxide  of  the  air,  during  the  precipitation  of  the  magnesia.  By 
the  use  of  a  large  test-tube,  as  above  described,  this  error  is  so  far 
reduced  as  to  be  insignificant.  Another  source  of  shortage  of 
lime  is  to  be  found  in  the  presence,  in  certain  materials,  of  small 
proportions  of  lime  in  a  form  insoluble  in  dilute  acid." 

In  determining  lime  in  cement  rock  or  in  cement  mixtures  made 
from  clay  containing  calcium  silicates  this  method  always  gives 
low  results  for  the  above  reason.  To  use  the  method  on  such 
material  it  is  necessary  to  determine  a  "correction  factor"  by  com- 
parison between  the  lime  found  by  this  method  and  that  on  page 
189,  in  a  series  of  standard  samples.  By  subtracting  the  lower 
from  the  higher  results,  a  constant  is  obtained  which  is  to  be  add- 
ed to  all  results  obtained  by  titration  with  the  acid  and  alkali. 

METHODS  FOR  CLAY. 

Silica. 

Finely  grind  the  sample  of  clay  and  heat  at  100°  to  110°  C.  for 
one  hour  in  an  air-bath.  Transfer  I  gram  of  the  dried  clay  to  a 


262  PORTLAND 

fairly  large  platinum  crucible.  Mix  with  it  by  stirring  with  a 
smooth  glass  rod  10  grams  of  sodium  carbonate  and  a  little  so- 
dium nitrate.  Heat  over  a  Bunsen  burner,  gently  at  first,  for  a 
few  minutes  and  then  to  quiet  fusion  over  a  blast  lamp.  Run  the 
fused  mass  well  up  on  the  sides  of  the  crucible  and  allow  to  cool. 
Nearly  fill  the  crucible  with  hot  water  and  set  on  the  hot  plate  for 
a  few  minutes.  Pour  the  solution  and  as  much  of  the  mass  as  has 
become  detached  from  the  crucible  into  a  casserole  or  better  a 
platinum  dish.  Repeat  this  treatment  until  the  mass  has  become 
thoroughly  disintegrated.  Treat  what  remains  in  the  crucible 
with  dilute  hydrochloric  acid  and  pour  the  acid  into  the  casserole 
or  dish.  Clean  out  the  crucible  with  a  rubber-tipped  rod  and  after 
acidifying  with  hydrochloric  acid  evaporate  the  contents  of  the 
casserole  to  dryness.  Proceed  as  in  A  or  B. 

A.  Heat  in  an  air-bath  at  110°  C.  for  one  hour,  or  until  all  odor 
of  hydrochloric  acid  has  vanished.     Cool,  moisten  the  mass  with 
dilute  hydrochloric  acid,  add  a  little  water  and  again  evaporate 
to  dryness.    Now  add  30  cc.  of  dilute  hydrochloric  acid,  digest  at 
a  gentle  heat  for  a  few  moments  and  add  100  to  150  cc.  of  hot 
water.    Allow  to  stand  a  few  minutes  on  the  hot  plate  and  filter. 
Wash  the  residue  thoroughly  with  hot  water,  ignite  over  a  Bun- 
sen  burner  until  all  carbon  is  burned  off,  and  then  for  five  min- 
utes over  a  blast  lamp,  and  weigh  as  SiO2. 

B.  The  residue,  without  further  heating,  is  treated  at  first  with 
10  cc.  of  dilute  HC1.    The  dish  is  then  covered  and  digestion  al- 
lowed to  go  on  for  10  minutes  on  the  bath,  after  which  the  solu- 
tion is  diluted  slightly,  filtered,  and  the  separated  silica  washed 
thoroughly  with  hot  water.     The  filtrate  is  again  evaporated  to 
dryness,  the  residue,  without  further  heating,  taken  up  with  acid 
and  water,  and  the  small  amount  of  silica  it  contains  separated  on 
another  filter  paper.     The  two  papers  containing  the  residue  are 
transferred  wet  to  a  weighed  platinum  crucible,  dried,  ignited, 
first  over  a  Bunsen  burner  until  the  carbon  of  the  filter  is  com- 
pletely consumed,  and  finally  over  the  blast  for  15  minutes.    The 
precipitate  is  then  weighed  as  SiO2.    This  precipitate  is  more  or 
less  contaminated  by  iron  oxide  and  alumina.     In  accurate  work 
the  amount  of  these  must  be  determined  in  the  following  manner 
and  deducted  from  the  weight  of  SiO2  as  found  above.     Moisten 


ANALYTICAL  METHODS  263 

the  weighed  silica  with  a  few  drops  of  dilute  sulphuric  acid  and 
half  fill  the  crucible  with  hydrofluoric  acid.  Evaporate  to  dryness 
by  placing  over  a  burner  in  an  inclined  position  so  that  the  low 
flame  plays  upon  the  side  of  the  crucible  and  the  evaporation  takes 
place  only  from  the  surface.  Ignite  and  weigh.  The  difference 
between  the  two  weights  is  the  silica,  SiO2. 

Ferric  Oxide  and  Alumina. 

Add  a  few  drops  of  bromine  water  and  heat  the  filtrate  from 
the  silica,  which  should  measure  about  150  cc.,  to  boiling,  and 
add  ammonia  in  slight  but  distinct  excess ;  boil  for  a  few  moments 
and  allow  the  precipitate  to  settle.  Filter  and  wash  several  times 
with  hot  water.  Remove  the  filtrate  from  under  the  funnel  and 
dissolve  the  precipitate  of  iron  and  alumina  in  a  mixture  of  15  cc. 
of  dilute  nitric  acid  and  15  cc.  of  cold  water,  by  pouring  back 
and  forth  through  the  filter  as  long  as  any  precipitate  remains. 
Wash  the  filter  paper  well  with  cold  water,  dry,  place  in  the 
weighed  platinum  crucible  containing  the  residue  from  the  puri- 
fication of  the  silica  if  this  has  been  done,  and  set  aside.  Repre- 
cipitate  the  iron  and  alumina  in  the  filtrate  as  before  by  adding  a 
slight  but  distinct  excess  of  ammonia,  filter,  and  wash  once  with 
hot  water.  Place  in  the  crucible  with  the  other  paper  and  ignite, 
using  the  blast  as  in  determining  silica  and  weigh  as 

Fe2O3  +  Al2O3(TiO2  +  P2O5  +  Mn8O4). 

Determine  the  ferric  oxide  in  the  precipitate  as  in  A,  B  or  C 
below  and  subtract  the  amount  from  this  weight;  the  difference 
will  be  the  Al2O3(TiO2  +  P2O5  +  Mn3OJ. 

A.  Fuse  the  ignited  precipitate  with  sodium  carbonate,  treat  the 
fused  mass  with  hot  water  and  wash  it  out  into  a  small  beaker, 
allow  the  residue  to  settle  and  decant  off  the  clear  supernatant 
liquid  through  a  small  filter,  leaving  the  residue  in  the  bottom  of 
the  beaker.  Wash  the  filter  paper  once  and  pour  a  little  hot  con- 
centrated hydrochloric  acid  through  the  filter  into  the  beaker  con- 
taining the  residue.  Heat  gently,  but  do  not  boil.  When  all  the 
residue  is  dissolved,  determine  the  iron  in  the  solution  by  re- 
duction with  stannic  chloride  and  titration  with  potassium  bichro- 
mate as  directed  on  page  196. 


264  PORTLAND 

B.  The  precipitate  is  fused  with  3  or  4  grams  of  potassium  bi- 
sulphate  at  a  very  low  temperature  and  the  melt  is  dissolved  in 
water  acidified  with  sulphuric  acid.    The  solution  is  then  reduced 
with  zinc  or  hydrogen  sulphide,  (preferably  the  latter  since  clays 
sometimes  contain  considerable  titanic  oxide),  and  the  iron  deter- 
mined as  directed  on  page  190. 

C.  Brush  the  ignited  precipitate  into  a  small  beaker,  cover  with 
a  mixture  of  6  cc.  of  water  and  16  cc.  of  concentrated  sulphuric 
acid,  and  covering  with  a  watch  glass,  digest  on  a  hot  plate  or 
sand-bath  until  all  dissolves,  except  possibly  a  residue  of  silica. 
Filter,  if  necessary,  and  determine  the  iron  by  reduction  with  zinc 
and  titration  with  standard  permanganate  as  directed  on  page  171. 

Lime. 

Heat  the  filtrate  from  the  iron  and  alumina  to  boiling  and  add 
an  excess  of  a  saturated  solution  of  ammonium  oxalate.  Stir  and 
boil  for  a  few  minutes  and  set  aside  for  several  hours  to  allow 
the  complete  precipitation  of  the  lime.  Filter,  wash,  dry,  and  ig- 
nite over  a  blast  lamp  until  the  weight  is  constant.  Weigh  as  cal- 
cium oxide,  CaO. 

Magnesia. 

To  the  filtrate  from  the  calcium  oxalate  add  sufficient  hydro- 
chloric acid  to  make  it  slightly  acid  and  then  30  cc.  of  sodium 
phosphate  solution.  Concentrate  the  solution  to  about  300  cc.  by 
evaporation  and  cool.  Then  add  ammonia  drop  by  drop,  with 
constant  stirring  until  the  liquid  is  slightly  ammoniacal  and  the 
precipitate  begins  to  form.  Stop  adding  ammonia  and  stir  for 
five  minutes,  then  add  one-tenth  the  volume  of  the  liquid  of  strong 
ammonia  and  continue  the  stirring  for  five  minutes  more.  Allow 
the  solution  to  stand  in  a  cool  place  over  night,  filter,  wash  with 
a  mixture  of  1000  cc.  water,  500  cc.  ammonia  (sp.  gr.  0.96),  and 
150  grams  ammonium  nitrate.  Dry,  ignite  (do  not  use  the  blast 
lamp),  and  weigh  as  magnesium  pyrophosphate,  Mg2P2O7.  Mul- 
tiply this  by  0.36190  for  magnesium  oxide,  MgO. 

Notes. 

Clay  is  practically  unacted  upon  by  hydrochloric  acid  and  re- 
quires fusion  with  alkaline  carbonates  for  its  decomposition. 


ANALYTICAL  METHODS  265 

Should  the  solution,  on  evaporation  to  dryness,  show  a  ten- 
dency to  climb  the  sides  of  the  dish,  greasing  the  latter  lightly 
with  vaseline  or  paraffin  will  remove  the  difficulty. 

The  amounts  of  lime  and  magnesia  in  clays  are  small,  so  that 
the  filtrate  and  washings  from  the  second  ammonia  precipitation 
of  the  iron  and  alumina  may  be  rejected  and  the  lirne  and  mag- 
nesia determined  in  the  first  filtrate  only.  For  the  same  reason 
it  is  unnecessary  to.  reprecipitate  the  calcium  oxalate,  although  the 
solution  is  largely  contaminated  by  sodium  salts  from  the  alka- 
line fusion. 

Determination  of  Free,  Hydrated  and  Combined  Silica.1 

To  ascertain  how  mucn  of  the  silica  found  exists  in  combina- 
tion with  the  bases  of  the  clay,  how  much  as  hydrated  acid,  and 
how  much  as  quartz  sand  or  as  a  silicate  present  in  the  form  of 
sand,  proceed  as  follows  \- 

Let  A  represent  silica  in  combination  with  the  bases  of  the  clay. 

Let  B  represent  hydrated  silicic  acid. 

Let  C  represent  quartz  sand  and  silicates  in  the  form  of  sand, 
e.  g.,  feldspar  sand. 

Dry  2  grams  of  the  clay  at  a  temperature  of  100°  C.,  heat  with 
sulphuric  acid,  to  which  a  little  water  has  been  added,  for  eight 
or  ten  hours,  evaporate  to  dryness,  cool,  add  water,  filter  out  the 
undissolved  residue,  wash,  dry,  and  weigh  (A  +  B  +  C).  Then 
treat  it  with  sodium  carbonate.  Transfer  it,  in  small  portions  at  a 
time,  to  a  boiling  solution  of  sodium  carbonate  contained  in  a 
platinum  dish,  boil  for  some  time  and  filter  off  each  time,  still  very 
hot.  When  all  is  transferred  to  the  dish,  boil  repeatedly  with 
strong  solution  of  sodium  carbonate  until  a  few  drops  of  the 
liquid  finally  passed  through  the  filter  remain  clear  on  warming 
with  ammonium  chloride.  Wash  the  residue,  first  with  hot  water, 
then  (to  insure  the  removal  of  every  trace  of  sodium  carbonate 
which  may  still  adhere  to  it)  with  water  slightly  acidified  with 
hydrochloric  acid,  and  finally  with  water.  This  will  dissolve 
(A  +  B)  and  leave  a  residue  (C)  of  sand,  which  dry,  ignite,  and 
weigh. 

To  determine  (B),  boil  4  or  5  grams  of  clay  (previously  dried 

1  Cairns'  Quantitative  Chemical  Analysis,  page  68. 

2  Compare  Fresenius'  Quantitative  Analysis,  sth  Ed.,  1865,  sec.  236. 


266  PORTLAND   CEMENT 

at  100°  C.)  directly  with  a  strong  solution  of  sodium  carbonate 
in  a  platinum  dish  as  above,  filter  and  wash  thoroughly  with  hot 
water.  Acidify  the  filtrate  with  hydrochloric  acid,  evaporate  to 
dryness,  and  determine  the  silica  as  usual.  It  represents  (B)  or 
the  hydrated  silicic  acid. 

Add  together  the  weights  of  (B)  and  (C),  thus  found,  and 
subtract  the  sum  from  the  weight  of  the  first  residue  (A+B+C). 
The  difference  will  be  the  weight  of  (A)  or  the  silica  in  combina- 
tion with  the  bases  of  the  clay. 

If  the  weight  of  (A+B  +  C)  found  here  to  be  the  same  as 
that  of  the  silica  found  by  fusion  in  a  similar  quantity  in  the 
analysis  of  the  clay,  the  sand  is  quartz,  but  if  the  weight  of 
(A  +  B+C)  be  greater,  then  the  sand  contains  silicates. 

The  weight  of  the  bases  combined  with  silica  to  form  silicates 
can  be  found  by  subtracting  the  weight  of  total  silica  found  in  i 
gram  in  the  regular  analysis,  from  the  weight  of  (A+B  +  C) 
in  i  gram. 

Notes. 

The  following  scheme  is  much  less  trouble  than  that  described 
above  and  gives  the  silica  present  as  sand  and  silicates  undecom- 
posable  by  sulphuric  acid  and  that  in  combination  with  the 
alumina  or  combined. silica. 

Heat  1.25  grams  of  the  finely  ground  and  dried  (at  100°  C.) 
clay  with  15  cc.  of  concentrated  sulphuric  acid  to  near  the  boiling- 
point  of  the  acid  and  digest  for  from  ten  to  twelve  hours  at  this 
temperature.  Cool,  dilute  and  filter.  Wash  and  ignite  the  residue 
to  a  constant  weight.  Call  this  weight  A.  After  weighing  brush 
the  residue  which  consists  of  silica  present  as  sand  and  undecom- 
posable  silicates  and  silica  from  the  decomposition  of  the  silicates 
of  alumina,  into  an  agate  mortar,  grind  very  finely  and  weigh  0.5 
gram  of  it  into  a  platinum  dish  containing  50  cc.  of  boiling  caustic 
potash  solution  (of  1.125  SP-  gr-)-  Boil  for  five  minutes,  filter, 
wash,  first  with  hot  water  and  then  with  water  containing  a  little 
dilute  hydrochloric  acid  and  then  again  with  hot  water,  dry  and 
ignite  to  a  constant  weight.  Call  this  weight  B.  Multiply  A  by 
0.4  (to  correct  the  1.25  grams  of  clay  used  to  correspond  to  the 
0.5  gram  of  the  residue  taken  for  treatment  with  caustic  potash 


ANALYTICAL  METHODS  267 

solution)  and  subtract  B  from  the  product.     Multiply  the  differ- 
ence by  200  for  the  per  cent,  of  silica  combined  with  alumina  in 
the  clay.     This  deducted  from  the  total  silica  found  by  analysis 
gives  the  silica  as  sand  and  undecomposable  silicates. 
Determination  of  Coarse  Sand. 

In  examining  clay  to  be  used  for  cement  manufacture,  it  is  not 
so  important  to  know  the  chemical  condition  in  which  the  silica 
exists  as  its  physical  state,  i.  e.,  whether  the  sand  grains  are  large 
or  small.  Pure  quartz  sand  if  sufficiently  finely  powdered  will 
combine  with  lime  at  the  temperature  of  the  rotary  kiln,  so  that 
what  is  most  requisite  in  clay  to  be  used  for  cement  manufacture 
is  that  the  sand  shall  be  present  in  fine  grains.  To  test  the  clay, 
along  this  line,  weigh  100  grams  of  clay  into  a  beaker  and  wet 
with  water.  Triturate  to  a  thin  slip  with  a  glass  rod  and  wash 
into  a  No.  100  test  sieve.  Now  place  the  sieve  under  the  tap  and 
wash  as  much  of  the  clay  as  possible  through  the  meshes  of  the 
sieve  with  a  gentle  stream  of  water.  Dry  the  sieve  on  a  hot  plate 
and  brush  out  the  dry  residue  failing  to  pass  through  it  on  to  the 
balance  pan  and  weigh.  The  weight  in  grams  gives  the  percent- 
age of  the  clay  failing  to  pass  a  No.  100  sieve.  The  clay  may  also 
be  tested  in  a  similar  manner  on  the  No.  200  sieve  and  the  residues 
may  be  subjected  to  chemical  analysis. 

Marls  are  examnied  by  the  same  method  to  determine  fineness. 
Determination  of  Water  of  Combination. 

Should  the  clay  contain  very  little  organic  mater,  iron  pyrites 
or  calcium  carbonate,  heat  i  gram  of  the  previously  dried  cement 
for  twenty  minutes  to  a  bright  redness  over  a  Bunsen  burner. 
The  loss  in  weight  will  represent  the  water  of  combination.  If, 
however,  the  clay  contains  much  organic  matter,  calcium  carbon- 
ate or  iron  pyrites,  the  water  of  combination  should  be  determined 
by  absorption  in  a  weighed  calcium  chloride  tube  as  described 
for  cement  analysis  on  page  208. 

Many  chemists  simply  heat  i  gram  of  dried  clay  over  a  blast 
for  twenty  minutes  reporting  the  loss  of  weight  as  loss  on  igni- 
tion. This  loss,  of  course,  comes,  from  combined  water  and  car- 
bon dioxide  driven  off  (from  the  decomposition  of  carbonates), 
organic  matter  burned  and  iron  pyrites  changed  from  iron  sul- 
phide, FeS2,  to  ferric  oxide. 


268  PORTLAND  CEMENT 

Sulphur  and  Iron  Pyrites. 

For  the  determination  of  sulphur  in  clay,  proceed  as  directed  for 
determining  this  constituent  in  cements  by  fusion  with  sodium 
carbonate  and  potassium  nitrate.  Multiply  the  weight  of  barium 
sulphate  by  0.25845  and  report  as  iron  pyrites,  FeS2,  or  by  0.13734 
and  report  as  sulphur. 

RAPID   DETERMINATION   OF   SILICA,   IRON    OXIDE 
AND  ALUMINA  AND  LIME. 

Weigh  0.5  gram  of  the  finely  ground  sample  of  clay  into  a 
platinum  crucible  and  mix  with  it  intimately,  by  stirring  with  a 
glass  rod  rounded  at  the  ends,  one  gram  of  precipitated  calcium 
carbonate  such  as  is  used  for  alkali  determinations  and  one-half 
gram  of  finely  powdered  dry  sodium  carbonate.  The  mixing  must 
be  thorough.  Brush  off  the  rod  into  the  crucible  with  a  camel's 
hair  brush  and  place  the  covered  crucible  over  a  Bunsen  burner 
turned  low.  Gradually  raise  the  flame  till  the  full  heat  is  attained, 
keep  at  this  temperature  for  2  or  3  minutes,  and  then  remove  to 
the  blast  lamp  and  ignite  strongly  for  5  minutes.  Cool  the  cruci- 
ble by  plunging  its  bottom  in  cold  water  and  place  it  on  its  side  in 
a  platinum  or  porcelain  dish  or  casserole.  Add  10  cc.  of  water 
and  10  cc.  of  dilute  (i-i)  acid.  As  soon  as  the  mass  is  dissolved 
out  of  the  crucible  remove  the  latter,  rinse  it  off  into  the  dish 
removing  any  solid  particles  with  a  policeman  and  evaporate  the 
solution  to  dryness.  Heat  the  dish  at  120°  C.  until  all  odor  of  acid 
has  disappeared.  Cool,  add  20  cc.  of  hydrochloric  acid  (i-i), 
cover  and  boil  a  few  minutes,  add  50  cc.  of  water,  boil  a  few  min- 
utes longer,  filter,  wash  and  ignite,  first  over  the  burner,  until 
carbon  is  all  burned  off,  and  then  over  the  blast  for  10  minutes. 
Cool  and  weigh  as  silica,  SiO2. 

Iron  Oxide  and  Alumina. 

Heat  the  filtrate  to  boiling,  after  adding  a  few  drops  of  bromine 
water,  add  ammonia  in  slight  but  distinct  excess  and  again  heat  to 
boiling.  Continue  boiling  for  two  or  three  minutes  and  after 
allowing  the  precipitate  to  settle,  filter  and  wash  once  with  hot 
water.  Invert  the  funnel  over'  the  beaker  in  which  the  precipita- 
tion was  made  and  wash  the  precipitate  back  into  this  with  a 
stream  of  hot  water  from  a  wash-bottle.  Dissolve  in  dilute  nitric 


ANALYTICAL  METHODS  269 

acid,  heat  to  boiling  and  reprecipitate  with  ammonia.  Boil  for  a 
few  minutes,  allow  the  precipitate  to  settle,  and  filter.  Wash  once 
with  hot  water,  ignite  (using  the  blast  finally)  and  weigh  as 
oxides  of  alumina  and  iron,  A12O3  +  Fe2O3. 

Lime. 

Weigh  another  sample  of  one  gram  into  a  platinum  dish  or  a 
large  crucible  and  add  10  cc.  of  dilute  sulphuric  acid(i-i)  and 
approximately  5  cc.  of  hydrofluoric  acid.  Heat  until  fumes  of 
sulphuric  acid  come  off  copiously.  Cool  and  wash  the  contents  of 
the  dish  into  a  250  cc.  beaker.  Heat  to  boiling  and  add  ammonia 
in  slight  but  distinct  excess.  Redissolve  the  precipitate  in  10  cc. 
of  a  10  per  cent,  solution  of  oxalic  acid,  and  dilute  to  200  cc. 
Precipitate  the  lime  with  calcium  oxalate  as  usual  and  determine 
as  directed  on  page  189. 

METHODS  FOR  GYPSUM  OR  PLASTER  OF  PARIS. 

Determination  of  Silica,  Iron  Oxide,  Alumina,  Lime  and  Mag- 
nesia. 

Weigh  0.5  gram  of  the  finely  ground  sample  into  a  platinum 
dish  or  porcelain  casserole  and  add  20  cc.  of  dilute  hydrochloric 
acid  (i-i).  Evaporate  to  dryness  and  heat  the  residue,  at  110°  C. 
until  all  odor  of  hydrochloric  acid  has  vanished  from  the  contents 
of  the  dish.  Cool  and  add  10  cc.  of  dilute  hydrochloric  acid,  cover 
with  a  watch  glass  and  heat  for  5  minutes.  Dilute  to  50  cc.  and 
heat  a  little  longer.  Filter,  wash  the  precipitate  well  with  hot 
water,  ignite  and  weigh.  Report  as  insoluble  silicious  matter  or 
proceed  as  follows :  Instead  of  igniting  and  weighing  fuse  this  in- 
soluble residue  after  burning  away  the  filter  paper  over  a  Bunsen 
burner  with  four  or  five  times  its  weight  of  sodium  carbonate  (us- 
ually from  0.2-0.5  gram  of  the  carbonate  is  enough),  run  the 
fused  mass  well  up  on  the  sides  of  the  crucible  and  cool  the  latter 
suddenly  by  dipping  its  bottom  in  cold  water.  Place  the  crucible 
in  a  dish  or  beaker  and  dissolve  out  the  fusion  in  a  little  dilute  hy- 
drochloric acid.  Evaporate  the  solution  to  dryness  and  heat,  at 
110°  C.,  until  all  odor  of  hydrochloric  acid  has  disappeared  from 
the  dry  mass.  Dissolve  in  a  little  hydrochloric  acid  and  water,  as 
before,  filter,  wash,  ignite  and  weigh  as  SiO2. 


270  PORTLAND   CEMENT 

Mix  the  above  filtrate  from  the  SiO2  with  that  from  the  "insolu- 
ble silicious  matter,"  heat  to  boiling,  precipitate  the  iron  and 
aluminum  as  oxides  with  ammonia  and  proceed  as  in  the  analysis 
of  cements  on  page  173. 

Determination  of  Sulphuric  Acid. 

Weigh  0.25  gram  of  the  finely  ground  sample  into  a  beaker  and 
dissolve  in  5  cc.  of  dilute  (i-i)  hydrochloric  acid,  by  the  aid  of 
heat.  Dilute  to  100  cc.  with  hot  water.  Digest  for  a  few  minutes 
and  filter.  Wash  the  paper  and  residue  thoroughly,  with  hot 
water,  until  the  filtrate  measures  about  250  cc.  Heat  this  latter 
to  boiling  and  add,  with  constant  stirring,  20  cc.  of  barium  chlor- 
ide solution,  also  boiling  hot,  and  stir  for  five  minutes.  Remove 
from  the  source  of  heat  and  allow  to  stand  o^er  night  in  a  warm 
place.  In  the  morning,  filter  through  a  double  filter  paper  or  a 
"Shimer  filter  tube"1  and  wash  well  with  hot  water.  Ignite 
(without  using  the  blast)  and  weigh  as  BaSO4.  This  weight 
multiplied  by  0.34291  gives  the  SO3  in  the  sample  or  by  0.62184 
the  (CaSO4)2  H2O  or  by  0.7375  tlle  CaSO4.  2H,O.  Do  not  for- 
get a  quarter  gram  sample  has  been  taken. 

Determination  of  Water. 

Weigh  one  gram  of  the  finely  ground  sample  in  a  weighed 
platinum  crucible  and  heat2  for  one  hour  at  100-105°  C.  Cool 
and  weigh.  The  loss  in  weight  represents  the  "moisture"  or 
" water  below  105°  C." 

Place  the  crucible  over  a  Bunsen  burner  and  heat  at  a  low  red 
temperature  for  thirty  minutes.  The  loss  in  weight  represents 
"water  of  combination"  or  "water  above  105°  C."  If  the  heating 
has  been  too  high,  some  sulphuric  acid  will  have  also  been  lost.  To 
check  this,  dissolve  the  sample  out  of  the  crucible,  after  ignition, 
with  hydrochloric  acid.  Dilute  to  about  100  cc.  and  filter  into  a 
200  cc.  flask.  Wash  well  with  hot  water  and  dilute  with  water  to 
the  mark.  Measure  of  this  volume  50  cc.  dilute  to  250  cc.  and  de- 
termine the  SO3  as  directed  previously.  If  loss  has  occurred, 
this  determination  will  give  a  lower  figure  than  the  other.  In 
this  case  deduct  the  difference  between  the  percentages  found  by 

1  See  page  206 

2  See  page  218. 


ANALYTICAL  METHODS  2/1 

the  two  trials  from  percentage  of  loss  in  weight  over  the  burner 
for  the  percentage  of  water  of  combination.  If  the  heating  of  the 
crucible  over  the  Bunsen  burner  has  been  done  at  a  heat  not 
higher  than  cherry  red  there  should  be  no  loss  of  sulphuric  acid, 
however. 

Determination  of  Carbon  Dioxide. 

Determine  carbon  dioxide  as  directed  on  page  215,  for  cement, 
using  the  evolution  method. 


PHYSICAL  TESTING. 


CHAPTER  XII. 


THE  INSPECTION  OF  CEMENT. 


Tests  to  be  Made. 

The  qualities  which  are  requisite  for  a  good  Portland  cement 
are  those  which  insure  that  concrete  made  from  it  shall  be  of 
sufficient  strength  to  withstand  any  and  all  strains,  stresses  and 
shocks  to  which  it  may  be  submitted,  not  only  when  first  made 
and  allowed  to  harden,  but  after  the  lapse  of  many  years.  The 
tests  now  applied  to  cement  all  aim  to  search  out  these  qualities, 
or  show  their  absence,  and  may  be  classed  under  two  general 
heads,  i.  e.,  those  designed  to  show  the  strength  of  concrete  made 
from  the  cement,  and  those  designed  to  show  its  endurance. 
Under  the  first  head  come  the  tests  for  tensile  strength,  com- 
pressive  strength,  fineness  to  which  the  cement  is  ground,  as  this 
influences  its  sand-carrying  capacity  and  hence  its  strength,  and 
time  or  rate  of  setting,  as  quick-setting  cement  may  not  give 
sufficient  time  for  proper  manipulation  of  the  concrete  and  slow- 
setting  cement  may  take  too  long  to  get  its  strength.  Under  tests 
for  endurance  come  the  various  so-called  soundness  tests,  and 
possibly  chemical  analysis  as  the  quantities  of  magnesia  and  of 
sulphur  trioxide  present  are  supposed  to  have  an  influence  upon 
endurance. 

Ordinarily  cement  is  tested  as  to  its: 

1 i )  Soundness. 

(2)  Time  of  setting. 

(3)  Tensile  strength  alone  (neat). 

(4)  Tensile  strength  with  sand. 

( 5 )  Fineness  to  which  it  has  been  ground. 

(6)  Specific  gravity. 

Other  tests  are  those  of  compressive  and  transverse  strength, 
adhesion,  abrasion,  etc. 


INSPECTION  OF  CEMENT  2/3 

Method  of  Inspection. 

It  is  now  the  custom  to  test  carefully  all  cement  to  be  used 
upon  important  work.  Most  of  the  large  cities  of  the  country 
maintain  well  equipped  laboratories  and  systematically  inspect  all 
cement  used  upon  the  various  municipal  works  undertaken  by 
them.  The  various  branches  of  the  government,  such  as  the  War, 
Navy  and  Treasury  Departments,  each  have  one  or  more  labora- 
tories where  the  cement  to  be  used  in  fortifications,  dry-docks, 
public  buildings,  etc.,  is  carefully  tested.  Various  private  labora- 
tories also  make  a  specialty  of  inspecting  the  cement  to  be  used  in 
big  buildings,  reservoirs,  retaining  walls,  etc., for  private  corpora- 
tions, while  the  railroads,  most  of  them,  have  well  equipped 
laboratories  for  testing  such  materials,  cement  among  them,  as 
they  purchase.  Cement  may  be  inspected  either  at  the  mill  before 
shipment,  or  at  the  place  where  it  is  to  be  used,  after  receipt.  The 
actual  tests  -of  course,  may  be  made  at  either  of  these  points,  or  the 
samples  can  be  properly  labelled  and  sent  some  distance  to  a  con- 
venient laboratory.  The  New  York  Rapid  Transit  Railroad 
(Subway)  Commission  pursued  the  former  of  these  two  plans 
and  inspected  the  cement  at  the  mill  itself.  The  Philadelphia 
Rapid  Transit  Company,  on  the  other  hand,  followed  the  latter 
plan  and  inspected  the  cement  as  received  in  Philadelphia.  Both 
plans  can  be  made  to  give  entire  satisfaction. 

Where  the  product  of  one  mill  alone  is  to  be  used  for  the  work 
the  testing  laboratory  may  be  located  at  the  mill  from  which  the 
cement  is  supplied.  Otherwise,  it  should,  of  course,  be  located  at 
some  convenient  point  to  which  samples  can  readily  be  sent. 

The  suggestion  has  been  made  to  have  the  cement  companies 
furnish  the  inspector  testing  appliances,  quarters,  etc.,  for  doing 
this  work.  This  seems  to  be  asking  rather  much  of  the  manufac- 
turers, as  their  laboratories  are,  most  of  them,  already  over- 
crowded and  the  presence  of  an  outsider,  in  the  one  part  of  the 
plant  where  trade  secrets  are  likely  to  be  exposed,  is  not  desirable. 
Inspection  at  the  Mill. 

Where  cement  inspection  is  done  at  the  mill,  certain  bins  are  set 
aside  by  the  proper  authority  at  the  cement  mill,  and  the  spouts 
leading  into  these  are  closed  by  means  of  a  wire  and  lead  seal  such 


2/4  PORTLAND  CEMENT 

as  is  used  in  closing  box  cars ;  the  idea  of  sealing  the  spouts  is  to 
prevent  the  bins  from  being  emptied  and  refilled  without  the 
knowledge  of  the  inspector.  Any  method  which  will  insure  against 
this,  such  as  sealing  wax  and  string  will  answer  as  well  as  the 
lead  seal  and  wire.  In  some  cases,  it  may  be  sufficient  to  rely 
upon  the  honesty  of  the  mill  authorities  and  to  merely  accept  their 
word  or  promise  that  the  bin  has  not  been  tampered  with.  Or 
an  affidavit  may  be  secured  from  the  stock-house  foreman  to  this 
effect. 

After  selecting  the  bin  and  insuring  against  its  being  emptied 
and  refilled,  it  must  be  carefully  sampled.  How  this  is  to  be  done 
will  depend  somewhat  upon  the  size  and  shape  of  the  bin.  Since 
cement  when  freshly  ground  and  hot  flows  not  unlike  a  liquid,  the 
the  cement  first  run  into  the  bin  will  be  almost  all  of  it  deposited 
in  a  layer  on  the  floor  of  the  bin.  For  this  reason,  the  means  used 
for  sampling  the  bin  must  be  such  that  the  cement  at  the  bottom  of 
the  bin  is  included  in  the  sample.  On  page  167,  a  rod  such  as  is 
used  by  the  inspectors  of  the  Baltimore  &  Ohio  Railroad  is  de- 
scribed. This  is  probably  as  satisfactory  as  any  sampling  device 
can  well  be.  The  taking  of  a  sample  from  the  floor  of  a  bin  may 
necessitate  the  use  of  a  sledge  hammer  to  drive  the  rod  through 
the  mass  of  cement  in  the  bin.  If  the  inspector  is  permanently 
located  at  the  mill,  the  sample  can  be  taken  easiest,  when  the  bin 
is  filled,  by  means  of  an  automatic  sampler  such  as  is  described  on 
page  226. 

The  importance  of  sampling  the  floor  of  a  bin  will  be  under- 
stood, when  it  is  known  that,  in  a  bin  of  unsound  cement,  a  sample 
taken  only  a  few  days  after  the  bin  has  been  filled  and  representing 
only  the  surface  layer  of  cement  will  often  be  sound,  while  one 
representing  the  bottom  layer  may  be  unsound  after  even  a 
month's  seasoning. 

The  bin  should  be  sampled  in  at  least  four  places — the  four  cor- 
ners— and  may  be  sampled  in  as  many  more  as  the  inspector  sees 
fit.  A  sample  drawn  from  the  four  corners  of  rectangular  shaped 
bins,  filled  by  a  spout  in  the  middle,  will  be  representative.  The 
feet  and  legs  of  the  man  taking  the  sample  may  be  protected  as 
he  walks  over  the  surface  of  the  cement  by  thrusting  them  in 


INSPECTION  OF  CEMENT  275 

clean,  new  cloth  cement  bags  (a  few  of  which  can  be  found 
around  all  mills)  and  tying  them  securely  around  the  legs  above 
the  knee.  The  cement  sample  should  be  placed  in  clean  cloth 
bags,  which  should  be  properly  closed  and  sealed  and  expressed 
or  conveyed  to  the  testing  laboratory.  If  the  inspecting  labora- 
tory is  located  at  the  mill,  paper  bags  or  tin  buckets  may  be  used 
for  this  purpose. 

The  objection  has  been  raised  to  the  use  of  cloth  bags,  that  an 
unsound  cement  would  probably  be  seasoned  sound  after  a  two  or 
three  days  journey  in  them  and  some  inspectors  use  tin  buckets  or 
cans,  with  tightly  fitting  covers,  for  this  purpose.  On  the  other 
hand,  if  an  unsound  sample  is  made  sound  by  exposure  in  cloth 
bags  after  a  few  days  journey  by  express,  the  inspector  may  rest 
assured  that  the  body  of  the  bin  will  be  seasoned  equally  well  by 
an  equally  long  journey  by  freight  in  a  box  car.  Also  cement 
often  leaves  the  mill  "slow  setting"  and  arrives  at  the  work"quick 
setting,"  so  that  shipment  of  a  sample  in  cloth  should  give  a  line 
on  the  likelihood  of  the  main  body  of  the  cement  doing  this. 

When  the  sample  arrives  at  the  testing  laboratory,  its  receipt 
is  properly  recorded  and  the  brand,  manufacturer,  bin,  date 
sampled,  etc.,  properly  recorded,  after  which,  to  readily  identify 
briquettes,  etc.,  it  is  given  a  running  number.  The  sample  is  then 
carefully  mixed,  and  a  sufficient  quantity  of  this  for  the  necessary 
tests  is  taken  and  passed  through  a  2O-mesh  sieve  to  remove 
lumps,  after  which  it  is  submitted  to  the  tests  called  for  by  the 
specifications.  The  large  sample  is  then  stored  away  for  future 
reference,  retests,  etc. 

When  the  results  of  the  tests  are  at  hand,  the  laboratory  noti- 
fies its  agent  at  the  mill,  who  in  turn  informs  the  authorities  of 
the  cement  company  that  such  and  such  a  bin  is  ready  for  ship- 
ment, and  when  cement  is  needed  it  is  also  the  duty  of  the  inspec- 
tor to  see  that  the  cement  is  packed  from  accepted  bins  and 
accepted  bins  only. 

This  system  usually  necessitates  the  holding  of  a  bin  for  from 
five  to  six  weeks,  if  the  specifications  call  for  a  28  day  test,  of 
about  two  weeks  if  only  the  7  day  test  is  relied  upon.  This  often 
puts  the  manufacturer  to  much  inconvenience  and  trouble,  but, 
from  the  standpoint  of  the  consumer,  seems  to  be  preferable,  since 


276  PORTLAND   CEMENT 

the  manufacturer  pays  for  the  storage  while  the  cement  is  being 
tested.  On  the  other  hand  the  manufacturer  has  the  satisfaction 
of  knowing  that,  after  the  cement  is  once  shipped,  it  is  off  his 
hands  for  good  and  all  with  no  chance  for  complaint  from  the 
purchaser. 

Inspection  on  the  Work. 

When  the  cement  is  inspected  as  it  arrives  at  the  work,  the  cars 
are  unloaded  and  sampled — one  bag  out  of  every  40  (or  one 
barrel  in  ten)  being  selected  and  a  sample  drawn  from  it  as  indi- 
cated on  page  166.  These  samples  may  be  either  mixed  or  kept 
separate  in  clean  paper  bags.  The  contents  of  each  car  should  be 
piled  in  such  a  way  that  it  may  be  kept  to  itself  and  marked  by 
a  properly  tagged  board  or  sign.  When  the  work  permits  the  use 
of  a  large  store  house,  this  should  be  divided  into  bins  holding  a 
carload,  150  barrels  or  600  bags.  The  cement  should  be  held  in 
storage  until  the  result  of  the  tests  are  known  when,  if  these  are 
satisfactory,  the  contractor  or  foreman  may  be  notified  that  he  can 
use  the  cement  from  such  and  such  a  pile  or  bin. 

When  a  car  of  cement  fails  to  pass  the  specifications,  the  manu- 
facturer is  usually  notified  at  once  that  such  cement  has  been 
found  unsatisfactory.  He  will  then  probably  ask  for  a  re-test, 
which  should  be  made  from  new  samples,  drawn  in  the  presence 
of  his  representatives,  and,  if  possible,  the  tests  also  should  be 
repeated  in  the  presence  of  this  representative.  If  this  latter  can 
not  be  done,  the  sample  should  be  divided  into  three  parts  and 
placed  in  tin  cans  or  fruit  jars  and  closed  up  tight.  One  of  these 
samples  should  be  tested  by  the  manufacturer  and,  unless  his  re- 
sults agree  with  those  of  the  consumer,  the  third  sample  should 
be  sent  to  some  reliable,  competent  third  party  with  the  agreement 
of  both  parties  to  stand  by  his  results. 

Should  the  cement  finally  be  found  unsatisfactory,  it  is  usually 
returned  to  the  manufacturer,  who  replaces  it  with  another  con- 
signment or  else  a  rebate  is  given  upon  it  and  it  is  used  on  some 
unimportant  part  of  the  job.  Unsound  cement  may  be  held  until 
it  has  been  seasoned  sound  and  quick  setting  cement  may  often  be 
made  slow  setting  by  a  small  addition  (0.5  per  cent)  of  plaster 
or  slaked  lime.  In  both  instances,  the  resulting  concrete  will  be 


INSPECTION  OF  CEMENT  277 

satisfactory  and  the  manufacturer  will  usually  be  willing  to  bear 
the  expense  of  storage,  or  addition  of  plaster  or  lime,  rather  than 
pay  the  double  freight  rate,  necessary  to  its  replacement  with 
other  cement.  When  the  cement  supplied  by  a  manufacturer  hab- 
itually fails  to  pass  the  specifications  under  which  it  is  sold,  he  de- 
serves little  consideration  from  the  engineer  or  inspector,  but, 
when  the  failure  of  a  brand  to  meet  specifications  is  a  rare  inci- 
dent, the  engineer  can  afford  to  be  lenient,  if  his  work  is  not  en- 
dangered thereby,  especially  if  the  average  quality  of  the  cement 
is  far  above  that  asked  for  by  him,  in  his  specifications. 

Uniform  Specifications  and  Methods  of  Testing. 

In  order  to  bring  about  uniformity  both  in  the  matter  of  in- 
spection and  of  the  specifications  under  which  cement  is  sold, 
committees  have  been  appointed  by  various  scientific  societies, 
chief  of  which  have  been  the  American  Society  for  Testing  Mate- 
rials and  the  American  Society  of  Civil  Engineers.  The  latter 
society  appointed  a  committee,  some  twenty  years  ago,  to  consider 
methods  of  testing  cement  and  received  its  report  in  1885.  Later, 
another  committee  was  appointed,  which  reported  January  2ist, 
1903.  This  report  was  amended  January  2Oth,  1904,  and  the 
methods  of  test  recommended  by  it  are  now  considered  the  stand- 
ard ones. 

The  American  Society  for  Testing  Materials  turned  its  atten- 
tion to  the  drafting  of  a  uniform  set  -of  specifications  for  cement, 
and  its  committee  reported,  June  I7th,  1904.  This  set  of  specifi- 
cations was  endorsed  by  The  American  Institute  of  Architects, 
The  American  Railway  Engineering  and  Maintenance  of  Way 
Association,  The  Association  of  American  Portland  Cement 
Manufacturers,  and  The  American  Society  of  Civil  Engineers, 
and  hence  may  be  considered  the  "Standard  Specifications/' 

In  the  following  sections  under  the  heading  "Specification"  are 
given  the  requirements  as  defined  by  the  above  set  of  specifications 
while  under  the  heading," Method  of  Operating  the  Test"  is  given 
the  method  of  testing  recommended  by  the  committee  of  the 
American  Society  of  Civil  Engineers  in  their  report. 


CHAPTER  XIIL 


SPECIFIC  GRAVITY. 


STANDARD  SPECIFICATIONS  AND  METHOD  OF  TEST 


Specification. — The  specific  gravity  of  the  cement,  thoroughly 
dried  at  100°  C.,  shall  be  not  less  than  3.10. 

B 


Fig.  65,  I,e  Chatelier's  Specific  Gravity  Apparatus. 

Method  of  Operating  the  Test. — The  determination  of  specific 
gravity  is  most  conveniently  made  with  Le  Chatelier's  apparatus. 
This  consists  of  a  flask  (D),  Fig.  65,  of  120  cu.  cm.  (7.32  cu.  ins.) 


SPECIFIC  GRAVITY  279 

capacity,  the  neck  of  which  is  about  20  cm.  (7.87  ins.)  long;  in 
the  middle  of  this  neck  is  a  bulb  (C),  above  and  below  which  are 
two  marks  (P)  and(E)  ;  the  volume  between  these  marks  is  20 
cu.  cm.  (1.22  cu.  ins.).  The  neck  has  a  diameter  of  about  9  mm. 
(0.35  in.),  and  is  graduated  into  tenths  of  cubic  centimeters  above 
the  mark  (P). 

Benzine  (62°  Baume  naphtha)  or  kerosene  free  from  water, 
should  be  used  in  making  the  determination. 

The  specific  gravity  can  be  determined  in  two  ways : 

(1)  The  flask  is  filled  with  either  of  these  liquids  to  the  lower 
mark  (E),  and  64  gr.  (2.25  oz.)  of  powder,  previously  dried  at 
1 00°  C.  (212°  F.)  and  cooled  to  the  temperature  of  the  liquid,  is 
gradually  introduced  through  the  funnel  (B)   [the  stem  of  which 
extends  into  the  flask  to  the  top  of  the  bulb  (C)  ] ,  until  the  upper 
mark  (P)  is  reached.    The  difference  in  weight  between  the  ce- 
ment remaining  and  the  original  quantity  (64  gr.)  is  the  weight 
which  has  displaced  20  cu.  cm. 

(2)  The  whole  quantity  of  the  powder  is  introduced,  and  the 
level  of  the  liquid  rises  to  some  division  of  the  graduated  neck. 
This  reading  plus  20  cu.  cm.  is  the  volume  displaced  by  64  gr.  of 
the  powder. 

The  specific  gravity  is  then  obtained  from  the  formula : 

Weight  of  Cement 
Specific  Gravity  =  =r^ —    — ,  xr  . — 

Displaced  Volume 

The  flask,  during  the  operation,  is  kept  immersed  in  water  in  a 
jar  (A),  in  order  to  avoid  variations  in  the  temperature  of  the 
liquid.  The  results  should  agree  within  o.oi. 

A  convenient  method  for  cleaning  the  apparatus  is  as  follows : 
The  flask  is  inverted  over  a  large  vessel,  preferably  a  glass  jar, 
and  shaken  vertically  until  the  liquid  starts  to  flow  freely ;  it  is 
then  held  still  in  a  vertical  position  until  empty ;  the  remaining 
traces  of  cement  can  be  removed  in  a  similar  manner  by  pouring 
into  the  flask  a  small  quantity  of  clean  liquid  and  repeating  the 
operation. 


280 


PORTLAND  CEMENT 


OTHER  METHODS. 
With  the  Schumann-Candlot  Apparatus. 

Another  form  of  apparatus  in  frequent  use,  particularly  abroad, 
for  taking  the  specific  gravity  of  cement  is  that  of  Schumann  as 
modified  by  Candlot  This  apparatus  (Fig.  66)  consists  of  a 


30 


20 


10 


c.c. 


Fig.  66,  Schumann  Candlot  Apparatus  for  Specific  Gravity. 

graduated  tube,  B,  terminated  by  a  bulb,  A.  This  tube  fits  tightly 
on  the  flask,  D,  by  means  of  a  ground  joint.  To  use  the  apparatus, 
paraffin,  turpentine,  or  benzine  is  introduced  into  the  detached  and 
inverted  tube,  B,  in  sufficient  quantity  to  bring  the  level  of  the 
liquid  above  the  zero  point  on  the  tube  when  the  latter  is  in  posi- 


SPECIFIC  GRAVITY  28l 

tion  on  the  flask,  D.  A  note  is  then  made  of  this  point,  the  tube 
is  inverted  and  the  flask  detached.  Into  the  latter  is  then  intro- 
duced a  known  weight  (usually  100  grams)  of  cement,  and  the 
flask  is  again  connected  with  the  tube.  The  whole  apparatus  is 
now  agitated  to  expel  air  bubbles,  then  set  in  an  upright  position 
and  the  new  height  to  which  the  liquid  rises  is  read.  The  differ- 
ence between  this  height  and  the  last  is  the  volume  of  liquid  dis- 
placed by  the  cement.  To  find  the  specific  gravity  of  the  cement 
divide  the  weight  of  cement  taken  by  the  volume  displaced,  the 
result  will  be  the  specific  gravity. 

Jackson's  Apparatus. 

Mr.  Daniel  D.  Jackson  has  devised  an  apparatus  for  the  deter- 
mination of  specific  gravity  which  is  shown  in  Fig.  67,  and  which 
he  describes  as  follows  :x 

Above  is  suspended  a  burette  with  graduations  about  9  inches 
(23  cm.)  long,  and  with  an  inside  diameter  of  about  ^4  inch  (0.6 
cm.).  This  is  connected  with  a  glass  bulb  approximately  5^ 
iches  (13  cm.)  long  and  i£4  inch  (4-5  cm.)  in  diameter. 

The  Erlenmeyer  flask  below  is  of  heavy  glass  and  contains 
a  ground  glass  stopper,  which  is  hollow,  and  has  a  neck  of  the 
same  bore  as  the  burette.  The  flask  has  a  capacity  of  exactly  200 
cubic  centimeters  up  to  the  graduation  on  the  neck  of  the  stopper. 

In  order  that  the  work  may  be  more  rapid,  the  burette  is  not 
graduated  in  cubic  centimeters  as  in  other  instruments  of  this 
nature,  but  is  made  to  read  directly  in  specific  gravity.  The  manu- 
facturer of  the  instrument  (Emil  Greiner,  78  John  Street,  New 
York  City),  makes  the  glass  bulb  of  such  a  size  that  from  the 
mark  on  the  neck  at  the  top  to  the  mark  on  the  burette  just  be- 
low the  bulb,  the  capacity  is  exactly  180  cubic  centimeters.  If  50 
grams  of  cement  are  taken,  this  mark  represents  a  specific  gravity 
of  2.50. 

200  (Capacity  of  flask). 
— 180  Capacity  of  bulb  to  ist  graduation. 

=  20  Volume  displaced  by  50  grams  of  cement. 
50  -~  20  =  2.50,  Specific  gravity. 

The  burette  is  graduated  for  every  0.05  in  specific  gravity  and 

ijour.  Soc.  Chem.  Ind.,  XXIII,  No.  u. 


282  PORTLAND   CEMENT 

five  equidistant  marks  are  placed  between  each  of  these  accurate 
graduations.  In  this  way  the  instrument  is  made  to  read  with 
accuracy  to  o.oi  in  specific  gravity. 


Fig.  67,  Jackson's  Specific  Gravity  Apparatus. 

The  accompanying  table  gives  the  calculations  used  in  the  orig- 
inal graduation  of  the  instrument : 


SPECIFIC  GRAVITY 


TABLE  XXIII.— FOR  GRADUATING  JACKSON'S  APPARATUS  FOR  THE  DE- 
TERMINATION OF  THE  SPECIFIC  GRAVITY  OF  CEMENT. 


Sp.  Gr. 

Reading, 
cc. 

Displace- 
ment. 

Sp.  Gr. 

Reading, 
cc. 

Displace- 
ment. 

2.50 

iSo.OO 

2O.OO 

3.01 

183.39 

16.61 

2-51 

180.08 

19.92 

3.02 

183.44 

16.56 

2.52 

180.16 

19.84 

3-03 

183-50 

16.50 

2-53 

180.24 

19.76 

304 

183.55 

16.45 

2-54 

180.31 

19.69 

3-05 

183.61 

16.39 

2-55 

180.39 

19.61 

3-o6 

183.66 

16.34 

2.56 

180.47 

19-53 

3.07 

183.71 

16.29 

2-57 

180.54 

19.46 

3-oS 

183.77 

16.23 

2.53 

180.62 

19.38 

3-°9 

183.82 

16.18 

2.59 

180.69 

I9-31 

3-10 

183.87 

16.13 

2.60 

180.77 

19.23 

3-II 

183.92 

16.08 

2.61 

180.84 

19.16 

3.12 

183.97 

16.03 

2.62 

180.92 

19.08 

3.13 

184.03 

J5-97 

2.63 

180.99 

19.01 

3-14 

184.08 

I5-92 

2.64 

181.06 

18.94 

3-15 

184.13 

15-87 

2.65 

181.13 

18.87 

3-16 

184.18 

15.82 

2.66 

181.20 

1  8.  80 

S-i? 

184.23 

15.77 

2.67 

181.27 

18.73 

3-18 

184.28 

15.72 

2.68 

181.34 

18.66 

3-19 

184.33 

15.67 

2.69 

181.41 

18.59 

3-20 

184.37 

15-63 

2.70 

181.48 

18.52 

3.21 

184.42 

15-58 

2.71 

181.55 

18.45 

3.22 

184.47 

I5-53 

2.72 

181.62 

18.38 

3.23 

184.52 

15.48 

2.73 

181.69 

18.31 

3.24 

184.57 

15-43 

2.74 

181.75 

18.25 

3.25 

184.62 

15-38 

2.75 

181.82 

18.18 

3.26 

184.66 

J5.34 

2.76 

181.88 

18.12 

3.27 

184.71 

15-29 

2.77 

181.95 

18.05 

3.28 

184.76 

15-24 

2.78 

182.01 

17.99 

3.29 

184.80 

15.20 

2-79 

182.08 

17.92 

3.30 

184.85 

15.15 

2.80 

182.14 

17.86 

3-31 

184.89 

15.11 

2.  Si 

182.21 

17-79 

3.32 

184.94 

15.06 

2.82 

182.27 

17-73 

3-33 

184.98 

15.02 

2.83 

182.33 

17.67 

3-34 

185-03 

14.97 

2.84 

182.39 

17.61 

3-35 

185.07 

14.93 

2.85 

182.46 

17-54 

3.36 

185.12 

14.88 

2.86 

182.52 

17.48 

3-37 

185.16 

14.84 

2.87 

182.58 

17.42 

3.38 

185.21 

M.79 

2.88 

182.64 

17-36 

3-39 

185.25 

14.75 

2.89 

182.70 

17.30 

3.40 

185.29 

14.71 

2.90 

182.76 

17.24 

3.41 

185.34 

14.66 

2.91 

182.82 

17.18 

3.42 

185.38 

14.62 

2.92 

182.88 

17.12 

3-43 

185.42 

14.58 

2-93 

182.94 

17.06 

3-44 

185.47 

14.53 

2.94 

182.99 

17.01 

3-45 

185.51 

14.49 

2-95 

183.05 

16.95 

3-46 

185.55 

14-45 

2.96 

183.11 

16.89 

3-47 

185.59 

14.41 

2-97 

183.16 

16.84 

3.48 

185.63 

!4.37 

2.98 

183.22 

16.78 

3-49 

185.67 

14-33 

2.99 

183.28 

16.72 

3-50 

185.71 

14.29 

3.00 

183.33 

16.67 

PORTLAND  CEMENT 


Method  of  Determination. — To  determine  the  specific  gravity 
of  a  cement  by  means  of  this  instrument : 

1.  Weigh  out  accurately  to  the  tenths'  place  of  decimals  50 
grams  of  the  dry  sample  of  cement. 

2.  Fill  the  bulb  and  burette  with  kerosene,  leaving  just  space 
enough  to  take  the  temperature  by  introducing  a  thermometer 
through  the  neck.     Remove  the  thermometer  and  add  sufficient 
kerosene  to  fill  exactly  to  the  mark  on  the  neck,  drawing  off  any 
excess  by  means  of  the  burette. 

3.  Run  into  the  unstoppered  Erlenmeyer  flask  about  one-half 
of  the  kerosene  in  the  bulb.    Then  pour  in  slowly  the  50  grams  of 
cement  and  revolve  to  remove  air  bubbles.    Run  in  more  kerosene 
until  any  adhering  cement  is  carefully  washed  from  the  neck  of 
the  flask,  and  the  kerosene  is  just  below  the  ground  glass. 

TABLE  XXIV.— CORRECTION  IN  SPECIFIC  GRAVITY  IN  VARIOUS  PORTIONS 
OF  THE  GRADUATED  SCALE  DUE  TO  CHANGE  IN  TEMPERATURE, 

FAHRENHEIT,  DURING  THE  DETERMINATION. 

Read  the  temperature  of  the  oil  in  the  bulb  before  the  determination,  and 
of  the  oil  in  the  flask  after  the  determination.  Add  the  correction  if  the 
temperature  of  the  oil  increases,  and  subtract  if  it  decreases. 


Change  in 
Temperature. 
Fahrenheit. 

2.50 
to 

2.60. 

2.60 
to 
2.70. 

2.70 
to 

2.80. 

2.8o 
to 
290. 

2.90 

to 

3-00. 

3.00 
to 

3.10. 

3-io 
to 

3-20. 

3.20 
to 

3-30. 

3-30 
to 

3.40. 

3-40 
to 
3-50. 

o.5° 

O.OI 

O.OI 

O.OI 

O.OI 

O.OI 

O.OI 

O.OI 

O.OI 

O.OI 

O.OI 

I.O 

O.OI 

o.or 

O.O2 

O.O2 

O.O2 

0.02 

0.02 

O.O2 

O.O2 

O.O2 

1-5 

O.O2 

O.O2 

O.O2 

0.02 

0.03 

0.03 

0.03 

0.03 

0.03 

0.03 

2.0 

0.03 

0.03 

0.03 

0.03 

0.03 

0.04 

0.04 

O.O4 

0.04 

0.05 

2-5 

0.03 

0.04 

0.04 

0.04 

O.O4 

0.05 

0.05 

0.05 

0.06 

O.O6 

3-° 

0.04 

0.04 

0.05 

0.05 

0.05 

o.os 

O.O6 

O.O6 

0.07 

O.O7 

3-5 

0.05 

0.05 

0.05 

O.O6 

O.O6 

0.06 

O.O7 

O.O7 

0.08 

0.08 

4.0 

0.05 

0.06 

O.o6 

O.o6 

O.O7 

0.07 

0.08 

0.08 

O.O9 

0.09 

4-5 

O.O6 

0.06 

O.O7 

0.07 

o.oS 

0.08 

0.09 

0.09 

O.  IO 

O.IO 

5-0 

O.O7 

0.07 

0.08 

0.08 

0.09 

0.09 

O.IO 

O.IO 

O.II 

0.12 

5-5 

O.O7 

0.08 

0.08 

0.09 

0.09 

O.IO 

O.IO 

O.II 

0.12 

0.13 

6.0 

0.08 

0.08 

O.O9 

O.IO 

O.IO 

0.  II 

O.I  I 

0.12 

O.I3 

0.14 

6-5 

0.08 

0.09 

O.IO 

O.TO 

O.  II 

O.I2 

0.12 

0.13 

0.14 

0.15 

7.0 

0.09 

O.IO 

O.I  I 

O.I  I 

0.  12 

0.13 

0.13 

O.I4 

0.15 

O.l6 

7-5 

0.10 

0.11 

O.  II 

O.I2 

0.13 

O.I4 

0.14 

0.15 

0.17 

0.17 

8.0 

0.10 

O.  II 

O.I  2 

O.I3 

0.14 

0.14 

0.15 

0.16 

0.18 

0.18 

8.5 

O.  II 

O.I2 

0.13 

0.14 

0.14 

0.15 

0.16 

0.17 

0.19 

O.2O 

9.0 

O.I2 

0.13 

0.14 

0.14 

0.15 

0.16 

0.17 

0.18 

0.20 

O.2I 

9-5 

0.12 

0.13 

0.14 

0.15 

0.16 

0.17 

0.18 

0.19 

O.2I 

O.22 

IO.O 

0.13 

0.14 

0.15 

0.16 

0.17 

0.18 

0.19 

O.2O 

O.22 

0.23 

4.  Place  the  hollow  ground  glass  stopper  in  position,  and  turn 


SPECIFIC  GRAVITY 


285 


it  to  fit  tightly.  Run  in  kerosene  exactly  to  the  200  cubic  centi- 
meter graduation  on  the  neck,  making  sure  that  no  air  bubbles 
remain  in  the  flask. 

5.  Read  the  specific  gravity  from  the  graduation  on  the  burette 
and  then  the  temperature  of  the  oil  in  the  flask,  noting  the  differ- 
ence betwen  the  temperature  of  the  oil  in  the  bulb  before  the  de- 
termination and  the  temperature  of  the  oil  in  the  flask  after  the 
determination. 

TABLE  XXV. — CORRECTION  IN  SPECIFIC  GRAVITY  IN  VARIOUS  PORTIONS 
OF  THE  GRADUATED  SCALE  DUE  TO  CHANGE  IN  TEMPERATURE, 

CENTIGRADE,  DURING  THE  DETERMINATION. 

Read  the  temperature  of  the  oil  in  the  bulb  before  the  determination  and 
of  the  oil  in  the  flask  after  the  determination.  Add  the  correction  if  the 
temperature  of  the  oil  increases,  and  subtract  it  if  it  decreases. 


Change  in 
Temperature. 
Centigrade. 

250 
to 

2.60. 

2.60 
to 
2.70. 

2.70 
to 

2.80. 

2.8o 
to 
2.90 

2.90 
to 
3-00. 

3.00 
to 
3-10 

3.10 
to 
3.20 

3.20 
to 
3-30 

3-30 
to 

3-40 

3,40 
to 
3-50 

0.2° 

0.00 

O.OI 

O.OI 

0.01 

O.OI 

O.OI 

O.OI 

O.OI 

O.OI 

O.OI 

0.4 

0.01 

O.OI 

O.OI 

O.OI 

O.OI 

O.OI 

O.OI 

O.OI 

0.02 

O.O2 

0.6 

O.OI 

O.O2 

O.O2 

O.O2 

O.O2 

O.O2 

0.02 

0.02 

0.02 

O.O2 

0.8 

0.02 

0.02 

O.O2 

O.O2 

O.O2 

0.03 

0.03 

0.03 

0.03 

0.03 

.0 

0.02 

0.03 

0.03 

0.03 

0.03 

0.03 

0.03 

0.04 

0.04 

O.O4 

1.2 

0.03 

0.03 

0.03 

0.03 

O.O4 

O.O4 

O.O4 

0.04 

0.05 

0.05 

1.4 

0.03 

0.04 

O.O4 

O.O4 

O.O4 

0.05 

0.05 

0.05 

0.06 

O.O6 

.6 

0.04 

O.O4 

0.04 

0.05 

0.05 

0.05 

0.05 

0.06 

0.06 

O.O7 

.8 

0.04 

005 

0.05 

0.05 

O.O6 

O.O6 

0.06 

0.06 

O.O7 

0.07 

2.0 

0.05 

0.05 

0.05 

O.O6 

O.O6 

O.O6 

O.O7 

0.07 

0.08 

0.08 

2.2 

0.05 

O.O6 

O.O6 

O.O6 

0.07 

O.O7 

0.08 

0.08 

0.09 

0.09 

2.4 

0.06 

O.O6 

O.O6 

O.O7 

O.O7 

0.08 

0.08 

0.09 

O.IO 

O.IO 

2.6 

O.O6 

O.O7 

O.O7 

0.07 

0.08 

0.08 

0.09 

0.09 

O.IO 

O.I  I 

2.8 

O.O7 

0.07 

0.08 

0.08 

O.O9 

0.09 

O.IO 

O.IO 

O.I  I 

O.  12 

3.0 

O.Oy 

0.08 

0.08 

0.09 

O.O9 

O.IO 

O.IO 

O.I  I 

0.12 

O.I  2 

3-2 

0.07 

0.08 

0.09 

0.09 

O.IO 

O.IO 

O.I  I 

0.12 

0.13 

O.I3 

3-4 

0.08 

0.09 

0.09 

O.IO 

O.  IO 

O.I  I 

0.  12 

0.12 

O.I3 

O.I4 

3-6 

0.08 

0.09 

O.IO 

O.IO 

O.I  I 

0.12 

0.12 

O.I3 

0.14 

0.15 

3-8 

0.09 

O.IO 

O.IO 

0.  II 

0.12 

0.12 

0.13 

0.14 

0.15 

0.16 

4.0 

0.09 

O.IO 

O.I  I 

0.12 

0.12 

0.13 

O.I4 

O.I4 

0.16 

0.17 

4.2 

O.  IO 

0.  II 

O.I  I 

0.12 

O.I3 

0.14 

O.I4 

0.15 

0.17 

0.17 

4-4 

O.  IO 

O.I  I 

0.12 

O.I3 

O.I3 

0.14 

0.15 

0.16 

0.17 

0.18 

4.6 

0.  II 

0.12 

0.  12 

0.13 

0.14 

0.15 

0.16 

0.17 

0.18 

0.19 

4.8 

O.I  I 

0.12 

0.13 

0.14 

0.15 

0.16 

0.16 

0.17 

0.19 

O.2O 

5-0 

0.12 

0.13 

0.14 

0.14 

0.15 

0.16 

0.17 

0.18 

O.2O 

0.21 

Make  a  temperature  correction  to  the  reading  of  the  specific 
gravity  by  the  use  of  the  accompanying  tables. 


286 


PORTLAND   CEMENT 


For  the  convenience  of  those  using  the  Centigrade  thermom- 
eter the  table  of  corrections  for  that  instrument  has  also  been  com- 
piled. 

It  is  thought  possible  that  the  variation  in  the  different  brands 
of  kerosene  might  be  sufficient  to  cause  an  error  in  the  determina- 
tion. A  collection  of  various  good  and  bad  kerosenes  was  made 
and  the  coefficient  of  expansion  of  each  sample  was  determined. 


Fig.  68,  Simple  Apparatus  for  Specific  Gravity. 

The  differences  in  expansion  found  were  entirely  within  the 
limit  of  error  of  the  determination. 

With  the  instrument  herein  described  the  time  required  to  make 
a  determination  is  about  ten  minutes,  and  the  accuracy  is  to  o.oi. 

Simple  Apparatus  for  Specific  Gravity. 

Fig.  68  shows  a  simple  form  of  apparatus  which  the  writer  has 
usually  used  for  taking  specific  gravity.  It  is,  of  course,  not  so 
neat  and  elegant  as  the  apparatus  devised  by  Mr.  Jackson,  but  it 


SPECIFIC  GRAVITY  287 

can  be  made  of  apparatus  found  about  the  laboratory  or  which 
can  be  purchased  from  the  stock  of  any  dealer.  Referring  to  the 
illustration  it  will  be  seen  that  in  place  of  the  special  form  of  bu- 
rette used  in  the  Jackson  apparatus,  a  50  cc.  automatic  pipette 
and  a  25  cc.  burette  graduated  in  1/?0  cc.  and  which  can  be  read 
to  1/40  cc.  are  used.  These  are  mounted  on  a  stand  and  connected 
with  a  reservoir  of  kerosene  on  a  shelf  above.  In  place  of  the 
special  flask  of  the  Jackson  apparatus  a  test  tube  drawn  out  near 
its  upper  end  to  about  j4  or  ^s-inch  in  diameter  is  used.  The 
test  tube  should  be  about  8  inches  long  and  I  inch  in  diameter, 
and  should  hold  about  100  cc.  It  is  then  drawn  out  about  6 
inches  from  the  bottom  and  a  mark  made  on  the  neck  by  covering 
the  latter  with  wax,  scraping  this  away,  in  a  ring  around  the 
drawn  out  part,  and  then  moistening  this  with  hydrofluoric  acid. 
Holes  about  i^  inches  deep  and  just  large  enough  to  hold  the 
tube  are  then  bored  in  the  board,  to  form  a  stand  for  the  test  tube. 
To  determine  the  specific  gravity  of  a  cement,  dry  the  tube  and 
run  in  a  pipette  full  of  kerosene.  Then  fill  from  the  burette  to 
the  mark.  This  will  require  about  75  cc.  or  possibly  more.  Now 
note  the  quantity  and  dry  the  flask.  Again  run  in  a  pipette  full 
of  kerosene,  placing  the  opening  of  the  pipette  \vell  down  in  the 
tube  so  as  not  to  wet  the  neck  of  the  latter.  Now  brush  into  the 
flask  25  grams  of  the  cement  to  be  tested,  after  carefully  weigh- 
ing the  latter  to  at  least  0.025  gram.  The  cement  should  be 
brushed  into  the  flask  very  gradually  and  any  particles  adhering 
to  the  upper  part  of  the  tube  brushed  into  the  neck.  Now  add 
kerosene  carefully  from  the  pipette  until  the  mark  on  the  neck 
is  reached.  The  volume  displaced  is  the  difference  between  this 
quantity  and  that  required  to  fill  the  empty  tube ;  and  the  specific 
gravity  is  the  weight  in  grams,  or  25,  divided  by  the  volume  dis- 
placed. For  example,  if  it  takes  81.35  cc.  to  fill  the  flasl^  to  the 
mark  when  empty  and  it  takes  73.3  to  fill  it  with  the  cement,  the 
specific  gravity  of  the  latter  will  be  25-^(81.35 —  73.3)  or 
25  -f-  8.05  =  3.11.  A  large  number  of  the  tubes  can  be  made  and 
the  volume  required  to  fill  each  etched  on  with  hydrofluoric  acid. 
A  dry  tube  will  then  always  be  ready.  The  cement  sample  should 
be  weighed  out  and  allowed  to  stand  15  minutes,  on  the  shelf  by 
the  large  bottle  of  kerosene.  This  avoids  the  necessity  of  making 


288 


PORTLAND  CEMENT 


corrections  for  temperature.     A  table  showing  the  specific  grav- 
ity corresponding  to  any  displacement,  is  given  below : 

TABLE  XXVI. — SHOWING  CONNECTION  BETWEEN  DISPLACEMENT  AND 
SPECIFIC  GRAVITY. 


Displacement, 
cc. 

Specific  Gravity. 

Displacement, 
cc. 

Specific  Gravity. 

7.500 

3-33 

8.000 

3-13 

7-525 

3.32 

8.025 

3.12 

7-550 

3.31 

8.050 

3." 

7-575 

3-30 

8.075 

3.10 

7.600 

3-29 

8.100 

3-09 

7-625 

3.28 

8.125 

3.08 

7.650 

3.27 

8.150 

3.07 

7.675 

3-26 

8.175 

3-o6 

7.700 

3-25 

8.200 

3-05 

7.725 

3-24 

8.225 

3-°4 

7.750 

3.23 

8.250 

3-03 

7-775 

3-22 

8.275 

3-02 

7.800 

3.21 

8.300 

3.01 

7-825 

3.20 

8.325 

3.00 

7.850 

3-19 

8.350 

2.99 

7-875 

3-17 

8.375 

2.98 

7.900 

3.16 

8.400 

2.98 

7-925 

3-15 

8.425 

2.97 

7-950 

3-H 

8.450 

2.96 

7-075 

3-13 

8-475 

2.95 

The  apparatus  must  be  set  in  a  place  free  from  sudden  changes 
of  temperature,  and  the  measuring  must  be  carefully  done.  The 
arrangement  is  well  adapted  for  use  where  only  a  few  determina- 
tions are  made  each  day. 

With  Specific  Gravity  Bottle. 

Where  the  apparatus  is  not  at  hand  for  the  above  methods,  the 
specific  gravity  may  be  taken  by  means  of  the  ordinary  specific 
gravity  bottle.  First  weigh  the  bottle,  empty,  then  fill  the  bottle 
with  water  and  weigh.  Then  dry  and  fill  with  benzine  and 
weigh.  Calculate  the  specific  gravity  of  benzine  from  the  formula 


~ 


where  x  =  sp.  gr.  of  benzine,  B  =  weight  of  bottle  full  of  ben- 
zine, W  =  weight  of  bottle  full  of  water,  and  />  =  weight  of  the 
empty  bottle. 


SPECIFIC  GRAVITY  289 

Now  introduce  a  weighed  portion  of  the  cement  into  the  bottle, 
fill  with  benzine,  and  weigh.  The  specific  gravity  of  the  cement 
may  then  be  found  by  the  formula 


B  +  C  —  D' 

where  B  =  weight  of  the  bottle  full  of  benzine,  C  =  weight  of 
the  cement.  D  =  weight  of  the  bottle  and  the  cement  and  the 
benzine,  ,v  =  specific  gravity  of  the  cement  as  found  above,  and 
X  =.  specific  gravity  of  the  cement.  Turpentine  or  paraffin  may 
be  used  in  place  of  benzine. 

OBSERVATIONS   ON  SPECIFIC   GRAVITY. 
Test  of  Little  Value  Alone. 

While  a  minimum  specific  gravity  clause  is  a  feature  of  every 
specification  for  Portland  cement,  there  is  probably  no  test  which 
taken  by  itself  might  lead  to  more  faulty  conclusions.  The  test 
of  itself  is  designed  to  detect  underburning  and  adulteration.  Un- 
fortunately for  any  conclusions  as  to  the  latter  we  might  draw, 
low  specific  gravity  is  often,  and  indeed  is  usually,  caused  by 
"aging"  of  the  cement,  so  that  to  reject  a  cement  because  of  a 
low  specific  gravity  may  be  to  reject  it  because  it  has  been  well 
seasoned.  It  is  now  generally  considered  that  cement  is  greatly 
improved  by  seasoning  as  the  water  and  carbon  dioxide  of  the 
air  react  with  any  free  or  loosely  combined  lime  in  the  cement, 
which  might  otherwise  cause  the  latter  to  be  unsound.  As  the 
cement  absorbs  these  constituents  from  the  air  its  specific  gravity 
becomes  less  and  less.  This  is  as  it  should  be,  since  the  specific 
gravity  of  calcium  carbonate  is  only  2.70  and  that  of  calcium  hy- 
drate only  2.08,  and  these  are  the  two  compounds  probably  form- 
ed during  seasoning. 

If  a  sample  which  has  been  kept  for  some  time  is  dried  at  100° 
C.,  its  specific  gravity  will  be  found  to  be  higher  than  it  was  in 
the  undried  condition,  but  still  not  as  high  as  when  it  was  freshly 
made.  If  this  sample  is  subjected  to  a  strong  ignition  in  a  plati- 
num crucible  over  a  good  blast  lamp,  its  specific  gravity  will  still 
further  increase  and  may  even  be  more  than  the  original  specific 
gravity  of  the  freshly  made  cement,  in  the  case  where  the  latter 
has  been  poorly  burned.  The  following  specific  gravities,  deter- 

10 


2QO 


PORTLAND   CEMENT 


mined  at  different  times,  of  a  number  of  Portland  cements,  illus- 
trate the  above  facts. 


Sample  No. 

Specific  Gravity. 

i 

2 

3 

4 

5 

\Vlien  made  

3-19 
3-U 
3-i6 
3-oS 
3-13 
3-i8 

3.21 
3.12 
3-l8 
3-04 
3-09 
3.21 

3-16 
3.10 

3-14 
3.08 
3.12 
3-18 

3-15 

3-°9 
3.12 

3-03 
.3-09 
3-15 

3.20 
3.08 

3-H 
3-04 
3-09 
3-19 

After  28  days,  dried  at  100°  C  

After  6  months,  dried  at  100°  C  •  • 

Reference  to  the  above  table  shows  that  samples  2,  4  and  5 
would  have  failed  to  come  up  to  the  standard  specific  gravity  spec- 
ification after  six  months,  and  yet,  briquettes  made  of  the  samples 
at  the  same  time  the  specific  gravity  determinations  were  made, 
showed  the  cement  to  be  at  its  best,  after  storage  for  that  length 
of  time. 

If  the  specific  gravity  of  cement  is  not  lowered  by  storage,  no 
seasoning  has  taken  place,  and  consequently  no  benefits  have  been 
derived  by  the  cement  from  aging.  Determinations  of  specific 
gravity  made  both  on  the  undried  and  dried  samples  of  cement 
may  give  us  an  insight  into  the  amount  of  seasoning  the  cement 
has  had.  If  the  two  results  agree  closely,  it  is  probable  that  the 
cement  is  fresh,  but,  if  these  results  vary  by  0.05  or  more,  we  may 
assume  that  the  cement  has  been  in  storage  for  a  few  weeks  at 
least. 

The  specific  gravity  determination  is  of  little  value  in  deter- 
mining whether  cement  has  been  underburned  or  not.  The  ex- 
perienced cement  chemist  at  the  mill  can  see  at  a  glance  by  look- 
ing at  the  clinker  if  it  is  underburned,  and  the  engineer  or  in- 
spector can  judge  better  by  the  test  for  soundness.  It  is  also  for 
the  reasons  given  above,  no  indication  of  adulteration.  If,  how- 
ever, the  specific  gravity  of  a  cement  is  low,  it  is  well  to  examine 
it  a  little  more  closely,  to  see  if  it  is  adulterated,  by  the  methods 
outlined  under  the  section  on  "Detection  of  Adulteration." 


CHAPTER  XIV. 


FINENESS. 

STANDARD  SPECIFICATION  AND  METHOD  OF  TEST. 


Specification. — It  shall  leave  by  weight  a  residue  of  not  more 
than  8%  on  the  No.  100,  and  not  more  than  25%  on  the  No.  200 
sieve. 

Method  of  Operating  the  Test. — Apparatus. — The  sieves  should 
be  circular,  about  20  cm.  (7.87  ins.)  in  diameter,  6  cm.  (2.36  ins.) 
high,  and  provided  with  a  pan.  ^  cm.  (1.97  ins.)  deep,  and  a 
cover. 

The  wire  cloth  should  be  woven  (not  twilled)  from  brass  wire 
having  the  following  diameters  : 

No.  100,  0.0045  m- ;  No.  2OO>  0.0024  in. 

This  cloth  should  be  mounted  on  the  frames  without  distortion : 
the  mesh  should  be  regular  in  spacing  and  be  within  the  follow- 
ing limits : 

No.  100,  96  to  100  meshes  to  the  linear  inch. 

No.  200,  1 88  to  200  meshes  to  the  linear  inch. 

Fifty  gram.  (1.76  oz.)  or  100  gr.  (3.52  oz.)  should  be  used  for 
the  test,  and  dried  at  a  temperature  of  100°  C.  (212°  F.)  prior  to 
sieving. 

Method. — The  thoroughly  dried  and  coarsely  screened  sample 
is  weighed  and  placed  on  the  No.  200  sieve,  which,  with  pan  and 
cover  attached,  is  held  in  one  hand  in  a  slightly  inclined  position, 
and  moved  forward  and  backward,  at  the  same  time  striking  the 
side  gently  with  the  palm  of  the  other  hand,  at  the  rate  of  about 
200  strokes  per  minute.  The  operation  is  continued  until  not 
more  than  one-tenth  of  i  per  cent,  passes  through  after  one  min- 
ute of  continuous  sieving.  The  residue  is,  weighed,  then  placed 
on  the  No.  100  sieve  and  the  operation  repeated.  The  work  may 
be  expedited  by  placing  in  the  sieve  a  small  quantity  of  large 
shot.  The  results  should  be  reported  to  the  nearest  tenth  of  I 
per  cent. 


292 


PORTLAND  CEMENT 


OTHER  METHODS. 
Methods  of  Sieving,  Sieves,  Etc. 

Where  many  sievings  have  to  be  made  every  day,  the  use  of  a 
sieve  without  top  and  bottom  is  the  general  plan.  In  this  case 
the  sieving  is  done  over  a  large  piece  of  paper  or  oil  cloth.  \Yhen 
it  is  desired  to  ascertain  if  the  operation  has  been  completed,  the 
material  on  the  paper  is  rolled  to  one  side,  by  lifting  the  edge  of 
the  paper,  thus  exposing  a  clean  surface  over  which  the  sifting 
may  be  continued  and  the  amount  passing  through  the  sieve  ob- 
served. An  experienced  operator  will  be  able  to  tell,  by  his  eye 
and  sense  of  time,  when  the  operation  is  finished,  without  re- 
course to  balance  and  weights.  In  place  of  striking  the  sieve 
against  the  palm  of  the  hand  some  operators  bounce  one  side  of  it, 
gently  up  and  down,  on  a  small  block  of  wood,  taking  care  not 
to  bounce  any  of  the  material  over  the  top  of  the  sieve.  The  use 
of  shot  also  greatly  hastens  the  operation  of  sieving,  as  the  bounc- 
ing of  these  latter,  on  the  wire  cloth  of  the  screen,  keeps  the 
meshes  of  the  latter  open.  To  separate  the  shot  from  the  coarse 
material  preparatory  to  weighing  the  latter,  pass  the  mixture 
through  a  10  or  20  mesh  screen. 


Fig.  69,  Balance  for  Fineness  Test. 

A  convenient  balance  for  use  in  making  sieve  tests  is  shown  in 
Fig.  69.  The  beam  is  graduated  into  Vioooo  °f  a  pound,  hence  if 
one-tenth  pound  (  =  about  45  grams)  is  taken  for  the  test  each 
of  the  small  divisions  on  the  beam  will  represent  o.i  per  cent,  resi- 
due. 


FINENESS  293 

At  the  mill  where  cement  is  usually  tested  fresh  as  it  comes 
from  the  grinders,  it  is  unnecessary  to  dry  it  at  100°  C.  before 
making  the  test,  but  when  inspecting  cement  which  has  been 
stored,  it  should  always  be  thoroughly  dried  before  making  the 
sieve  test.  If  both  specific  gravity  and  sieve  tests  are  to  be  made, 
enough  cement  should  be  dried  for  both  tests.  Descriptions  of 
various  forms  of  drying  ovens  are  given  on  page  218. 

When  tests  are  made  by  using  sieves  without  a  top  the  sides 
of  these  should  be  high  in  order  to  avoid  bouncing  the  material 
out  of  the  apparatus.  If  the  sieving  is  done  by  bouncing  the  sieve 
up  and  down  on  a  block  the  sides  of  the  sieve  should  be  at  least 
six  inches  high. 

Errors  in  Sieves. 

In  purchasing  sieves  for  making  the  fineness  test,  care  must  be 
exercised  to  see  that  they  are  within  the  limits  prescribed  by  the 
standard  rules,  for  there  are  many  so-called  standard  sieves  on  the 
market  which  are  anything  but  standard.  I  have  seen  a  No.  100 
test  sieve  bearing  the  name  of  a  well-known  firm,  which  makes  a 
specialty  of  supplying  apparatus  for  cement  testing,  that  was 
made  of  wire  cloth  containing,  to  the  linear  inch,  90  meshes  one 
way  by  93  the  other.  Not  only  may  standard  sieves  not  contain  the 
proper  number  of  meshes  but  the  wire  from  which  the  cloth  is 
woven  may  be  larger  or  smaller  than  the  size  called  for  in  the 
standard  method.  This  will  reduce  or  increase,  as  the  case  may 
be,  the  size  of  the  openings  of  the  sieve.  Not  only  may  the  sieves 
vary  from  the  standard  by  reason  of  incorrect  mesh,  but  also  by 
reason  of  irregular  spacing.  That  is,  the  wires  may  be  nearer  to- 
gether in  some  places  than  in  others,  leaving  large  openings  at  the 
latter  points  for  the  cement  to  drop  through. 

On  purchasing  sieves  they  should  be  examined  as  to  the  regu- 
larity of  the  spacing  by  holding  them  to  the  light  and  also  the 
number  of  meshes  to  the  inch  should  be  counted.  For  this  latter 
purpose,  small  magnifying  glasses  such  as  are  used  for  testing 
linen  are  convenient.  These  consist  of  a  small  lens,  mounted  on 
a  stand,  in  the  base  of  which  is  an  opening  exactly  one-half  inch 
square.  The  opening  is  placed  over  various  parts  of  the  sieve  and 
the  number  of  meshes  counted.  Where  such  an  instrument  is  not 


2Q4  PORTLAND   CEMENT 

at  hand,  an  opening  of  this  size  may  be  cut  in  a  piece  of  card- 
board and  the  meshes  counted  by  the  aid  of  a  small  reading  or 
pocket  magnifying  glass.  Sieves  may  also  be  calibrated  by  com- 
paring them  with  other  sieves  of  known  value.  Any  holes  or 
irregularities  in  test  sieves  may  be  stopped  up  with  solder. 

OBSERVATIONS  ON  FINENESS. 
Limitations  of  the  Sieve  Test. 

The  fineness  to  which  cement  is  ground  is  an  important  point. 
Since  cement  is  usually  used  with  sand,  the  strength  of  the  mor- 
tar increases  with  the  fineness  of  the  cement,  because  the  greater 
is  the  covering  power  of  the  cement,  i.  ev  the  more  parts  of 
cement  come  into  action  with  the  sand.  A  test  for  fineness  is 
nearly  always  included  in  cement  specifications,  as  the  indications 
from  a  fair  degree  of  fineness  coupled  with  proper  tensile 
strength,  neat,  are  that  the  cement  will  give  good  results  when 
used  with  sand. 

At  the  same  time  the  most  rigid  fineness  specification  could  be 
filled  by  a  cement  which  would  be  many  degrees  too  coarse.  Some 
of  the  older  specifications  could  be  easily  filled  by  a  product  which 
would  show  almost  no  setting  qualities  and  no  sand-carrying  ca- 
pacity. If  a  sample  of  clinker  is  crushed  in  an  iron  mortar  by  a 
pestle  and  sieved  as  fast  as  it  is  ground  through  a  loo-mesh 
screen,  a  product  will  be  obtained  100  per  cent,  of  which  will  pass 
a  loo-mesh  screen.  Many  of  the  older  specifications  call  for  only 
90  per  cent.  If  a  pat  is  made  of  this  cement  it  will  just  about 
cohere.  If,  however,  the  fine  particles  are  sieved  through  a  200- 
mesh  screen  and  the  flour  washed  off  the  coarse  particles  by  ben- 
zine and  the  latter  driven  off  by  heat,  the  product  will  still  all 
pass  a  loo-mesh  sieve,  and  yet  will  have  no  setting  properties.  If 
another  sample  is  ground  in  a  mortar  and  sieved  after  every  few 
strokes  of  the  pestle  through  a  2OO-mesh  screen,  it  will  all  pass  a 
2OO-mesh  sieve  and  yet  will  nevertheless  be  almost  worthless  as 
a  cement.  When  washed  free  from  its  flour  with  benzine  it  will 
just  about  hold  together.  In  the  writer's  laboratory  there  is  a 
Braun's  gyratory  muller  for  grinding  samples,  in  which  the  grind- 
ing is  done  by  an  enclosed  round  pestle  revolving  in  a  semi-hemi- 


FINENESS  295 

spherical  mortar.  In  the  bottom  of  the  mortar  is  a  hole  which  can 
be  stopped  by  a  plug.  The  grinding  may  be  done  in  two  ways, 
one  by  feeding  the  sample  into  the  hopper  in  the  cover  and  allow- 
ing it  to  work  its  way  out  at  the  bottom,  then  sieving  out  the  fine 
material  from  the  coarse,  and  returning  the  latter  through  the 
grinder,  and  so  on  until  all  has  passed  the  sieve.  The  other,  by 
placing  the  plug  in  the  bottom  of  the  mortar  and  allowing  the 
pestle  to  work  upon  the  material  until  the  latter  has  reached  the 
desired  fineness.  Two  samples  of  cement  were  prepared  from  the 
same  lot  of  clinker  by  these  methods.  One  sample,  the  one  made 
by  passing  the  clinker  through  the  muller  and  sieving  out  the  200- 
mesh  particles  after  each  grind,  would,  of  course,  all  pass  a  200 
mesh  sieve.  The  other  sample,  the  one  made  by  grinding  the 
whole  sample  to  the  desired  fineness  without  screening,  tested  96 
per  cent,  through  a  loo-mesh  sieve  and  76.5  per  cent,  through  a 
20O-mesh  sieve.  Sand  briquettes  were  made  of  these  two  lots  of 
cement  with  the  following  results. 

7  days.  28  days.  3  mos.      6  mos. 

Samples  made  by  lbs-  lbs-  lbs-         lbs- 

Grinding  and  screening  to  fineness  (  Broke  in     Broke  in     Broke  in 
(all  200  mesh) |      clips  ciips  clips 

Grinding  to  fineness  without  screening        215  295  324      3J8 

The  cementing  value  of  Portland  cement  depends  upon  the  per- 
centage of  those  infinitesimal  particles  which  we  call  flour.  No 
sieve  is  fine  enough  to  tell  the  quantity  of  these  present.  At  the 
same  mill  it  is  probable  that  the  sieve  test  is  relative  but  to  the 
engineer  who  is  called  upon  to  examine  the  product  of  many  mills 
using  different  systems  of  grinding  the  sieve  test,  is  hardly  to  be 
expected  to  give  the  relative  percentage  of  flour  in  each.  The 
product  of  the  Griffin  mill  and  of  the  ball  and  tube  mill  probably 
differ  much  in  the  percentage  of  flour  present,  even  when  testing 
the  same  degree  of  fineness  on  the  2OO-mesh  sieve.  Even  with 
the  ball  and  tube  mill  system  one  ball  mill  and  two  tube  mills 
would  probably  give  a  product  with  a  higher  percentage  of  flour 
than  one  tube  mill  and  two  ball  mills,  even  when  the  cement  was 
ground  to  the  same  sieve  test.  The  size  screen  on  the  ball  mills 
probably  also  influences  the  percentage  of  flour  in  a  product  of  a 
certain  fineness. 


296  PORTLAND   CEMENT 

DETERMINING  THE  FLOUR  IN  CEMENT. 

A  number  of  devices  have  been  proposed  for  determining  the 
flour  in  cement.  The  chief  difficulty  with  them  all  seems  to  be 
standardization.  Each  one  will  give  a  different  result  from  the 
other,  as  we  would  suppose,  for  there  is  no  specification  as  to 
what  is  meant  by  flour,  and  each  apparatus  takes  out  a  size  differ- 
ent from  the  other. 

Practically  all  of  these  forms  of  apparatus  depend  upon  the  sus- 
pension of  the  finer  particles  of  the  cement  in  benzene,  kerosene, 
water,  etc.  A  number  of  them  are  described  in  The  Engineering 
Record  of  August  2Oth,  1904,  page  234.  As  we  have  said,  the 
difficulty  with  all  of  them  is  that  each  would  report  a  different 
percentage  of  the  cement  as  flour.  Even  if  they  were  so  cali- 
brated as  to  give  concordant  results,  these  figures  would  mean 
nothing  more  than  the  sieve  test  carried  a  little  further.  We  do 
not  know  how  fine  cement  has  to  be  ground  in  order  to  "carry 
sand,"  although  we  know  that  it  must  be  ground  considerably  finer 
than  merely  sufficient  for  it  to  just  pass  the  2OO-mesh  sieve.  For 
experimental  purposes  it  is  highly  important  to  obtain  some  form 
of  apparatus  which  will  enable  the  finer  particles  of  the  cement  to 
be  sorted  out  and  graded,  in  order  that  the  point  of  fineness  at 
which  the  sand  carrying  capacity  begins  to  approach  that  of  or- 
dinary commercial  cements  may  be  determined.  Such  an  appara- 
tus, after  this  point  has  been  determined,  would  have  a  practical 
value,  because  of  two  cements  the  one  having  the  greatest  per- 
centage of  such  "active"  particles  would  be  the  best  ground. 

When  I  have  had  occasion  to  desire  to  know  the  percentage  of 
fine  particles  in  cement,  I  have  adopted  an  apparatus  modeled 
after  the  silt  cylinders  used  for  soil  analysis.  Fig.  70  shows  such 
an  apparatus.  It  consists  of  a  cylinder  of  at  least  300  mm.  height 
and  not  too  great  diameter  provided  writh  a  cork  or  stopper  for 
closing  it  and  a  syphon  for  drawing  off  the  liquid  and  suspended 
matter.  The  lower  end  of  the  syphon  is  closed  by  a  rubber  tube 
and  pinch-cock  and  the  upper  one  is  bent  as  shown.  Strips  of 
paper  or  file  marks  are  made. on  the  cylinder,  one  near  the  top 
and  the  other  exactly  200  mm.  below  this  one.  In  use,  100  grams 
of  cement  are  introduced  into  the  cylinder  and  the  latter  filled 


FINENESS 


297 


with  benzene  to  the  upper  mark  and  shaken  well.  It  is  then 
placed  on  a  block,  the  syphon,  which  should  be  full  of  benzene  in- 
serted until  its  opening  is  level  with  the  lower  mark,  and  exactly 
10  seconds  after  the  cylinder  was  placed  on  the  block  the  pinch- 
cock  is  to  be  opened  and  the  liquid  syphoned  off  to  the  lower 
mark.  This  process  is  repeated  until  the  liquid  above  the  lower 
mark  settles  practically  clear  in  10  seconds.  The  residue  in  the 


Fig.  70,  Apparatus  for  Determining  Flour. 

cylinder,  or  else  the  suspended  matter,  is  then  collected  on  a  filter 
and  its  weight  determined.  From  this  the  percentage  of  flour  is 
calculated  and  reported  as  "particles  having  a  settling  value  in 
benzene  of  less  than  20  millimeters  per  second."  These  can  be 
again  divided  into  two  portions,  by  allowing  15  seconds  to  settle, 
when  the  value  will  be  200  -f-  15  or  13^/3  mm.  per  second,  etc. 

If  desired,  the  size  of  the  largest  of  these  particles  can  then  be 
measured  under  the  microscope. 


298  PORTLAND   CEMENT 

If  sieves  smaller  than  2OO-mesh  are  desired,  it  is  probable  that 
they  could  be  made  by  electroplating  the  cloth  of  the  above  size 
with  nickel,  silver,  etc.,  and  measuring  the  openings  under  the 
microscope,  at  various  stages  of  the  process,  until  meshes  of  the 
proper  dimensions  are  obtained. 


CHAPTER    XV. 


TIME  OF  SETTING, 


STANDARD  SPECIFICATION  AND  METHOD  OF  TEST. 


Specification. — It  shall  develop  initial  set  in  not  less  than  thirt> 
minutes,  but  must  develop  hard  set  in  not  less  than  one  hour,  nor 
more  than  ten  hours. 

Normal  Consistency. 

Method. — This  can  best  be  determined  by  means  of  Vicat  Nee- 
dle Apparatus,  which  consists  of  a  frame  (K),  Fig.  71,  bearing  a 
movable  rod  (L,),  with  the  cap  (A)  at  one  end,  and  at  the  other 
the  cylinder  (B),  i  cm.  (0.39  in.)  in  diameter,  the  cap,  rod  and 
cylinder  weighing  300  gr.  (10.58  oz.).  The  rod,  which  can  be 
held  in  any  desired  position  by  a  screw  (F),  carries  an  indicator, 
which  moves  over  a  scale  (graduated  to  centimeters)  attached 
to  the  frame  (K).  The  paste  is  held  by  a  conical,  hard-rubber 
ring  (I),  7  cm.  (2.76  ins.)  in  diameter  at  the  base,  4  cm.  (1.57 
ins.)  high,  resting  on  a  glass  plate  (J)r  about  10  cm.  (3.94  ins.) 
square. 

In  making  the  determination,  the  same  quantity  of  cement  as 
will  be  subsequently  used  for  each  batch  in  making  the  briquettes 
(but  not  less  than  500  grams)  is  kneaded  into  a  paste,  as  describ- 
ed in  paragraph  39,  and  quickly  formed  into  a  ball  with  the  hands, 
completing  the  operation  by  tossing  it  six  times  from  one  hand  to 
the  other,  maintained  6  ins.  apart ;  the  ball  is  then  pressed  into  the 
rubber  ring,  through  the  larger  opening,  smoothed  off,  and  placed 
(on  its  large  end)  on  a  glass  plate  and  the  smaller  end  smoothed 
off  with  a  trowel ;  the  paste,  confined  in  the  ring,  resting  on  the 
plate,  is  placed  under  the  rod  bearing  the  cylinder,  which  is 
brought  in  contact  with  the  surface  and  quickly  released. 

The  paste  is  of  normal  consistency  when  the  cylinder  penetrates 
to  a  point  in  the  mass  10  mm.  (0.39  in.)  below  the  top  of  the  ring. 
Great  care  must  be  taken  to  fill  the  ring  exactly  to  the  top. 


300 


PORTLAND  CEMENT 


The  trial  pastes  are  made  with  varying  percentages  of  water 
until  the  correct  consistency  is  obtained. 
Time  of  Setting. 

Method. — For  this  purpose  the  Vicat  Needle,  which  has  al- 
ready been  described,  should  be  used. 

In  making  the  test,  a  paste  of  normal  consistency  is  molded  and 
placed  under  the  rod  (L),  Fig.  71,  as  described;  this  rod,  bearing 


Fig.  71,  Vicat  Needle. 

the  cap  (D)  at  one  end  and  the  needle  (H),  i  mm.  (0.039  m-)  m 
diameter,  at  the  other,  weighing  300  gr.  (10.58  oz.).  The  needle 
is  then  carefully  brought  in  contact  with  the  surface  of  the  paste 
and  quickly  released. 

The  setting  is  said  to  have  commenced  when  the  needle  ceases 
to  pass  a  point  5  mm.  (0.20  in.)  above  the  upper  surface  of  the 
glass  plate,  and  is  said  to  have  terminated  the  moment  the  needle 
does  not  sink  visibly  into  the  mass. 

The  test  pieces  should  be  stored  in  moist  air  during  the  test; 


TIME  OF  SETTING  3OI 

this  is  accomplished  by  placing  them  on  a  rack  over  water  con- 
tained in  a  pan  and  covered  with  a  damp  cloth  to  be  kept  away 
from  them  by  means  of  a  wire  screen ;  or  they  may  be  stored  in  a 
moist  box  or  closet. 

Care  should  be  taken  to  keep  the  needle  clean,  as  the  collection 
of  cement  on  the  sides  of  the  needle  retards  the  penetration,  while 
cement  011  the  point  reduces  the  area  and  tends  to  increase  the 
penetration. 

The  determination  of  the  time  of  setting  is  only  approximate, 
being  materially  affected  by  the  temperature  of  the  mixing  water, 
the  temperature  and  humidity  of  the  air  during  the  test,  the  per- 
centage of  water  used,  and  the  amount  of  molding  the  paste  re- 
ceives. 

OTHER  METHODS. 

The  test  proposed  by  General  Gilmore,  U.  S.  A.,  for  determin- 
ing setting  properties  is  the  one  most  used,  however,  in  this  coun- 
try. It  consists  in  mixing  cakes  of  neat  cement  from  2  to  3 
inches  in  diameter  and  J^  inch  thick  to  a  stiff  plastic  consistency 
and  observing  the  time  when  they  will  bear  a  needle  1/12  inch  in 
diameter  weighted  with  l/±  pound.  This  is  noted  as  the  beginning 
of  the  set.  These  pats  should  be  made  with  a  flat  top  so  as  not 
to  catch  the  edge  of  the  needle.  Trials  are  next  made  every  now 
and  then  with  a  1/24  inch  in  diameter  needle  weighted  with  one 
pound.  The  time  at  which  the  cake  is  sufficiently  firm  to  bear 
this  latter  needle  is  noted  as  the  end  of  the  set. 

The  Gilmore  needles,  or  wires,  are  much  more  convenient  to 
use  wrhere  many  samples  have  to  be  tested,  as  the  pats  themselves 
do  not  have  to  be  lifted  from  the  moist  closet  or  table,  in  order  to 
apply  the  needle.  While  the  Vicat  needle  unquestionably  is  a 
much  more  scientific  instrument  and  should  be  used  where  great 
nicety  is  required  in  making  the  test,  as  in  settling  disputes,  etc. ; 
still  for  ordinary  inspection  work,  where  all  that  is  needed  is  the 
assurance  that  the  cement  will  not  set  before  it  is  laid  in  position 
in  the  job,  and  that  after  it  is  so  placed  it  will  harden  in  a  rea- 
sonable time,  the  simpler  and  less  expensive  Gilmore  needles  will 
answrer  the  purpose  just  as  well  as  the  more  expensive  Vicat  ap- 
paratus. The  Gilmore  needles  are  the  ones  generally  used  by 


302 


PORTLAND   CEMENT 


both  manufacturers  and  engineers  in  determining  the  setting  time 
of  cement,  and  most  of  those  called  upon  to  test  and  use  cement 
are  familiar  with  the  terms  initial,  and  final  set  as  defined  by  these 
needles,  so  that  it  does  not  seern  to  have  been  a  very  wise  plan  on 
the  part  of  those  formulating  the  standard  rules  to  recommend 
that  the  test  be  made  with  the  Vicat  needle.  Setting  time  is  influ- 
enced by  so  many  things  besides  those  over  which  the  Vicat  needle 
has  control  that  the  personal  equation  is  as  much  an  element  in 
determinations  made  with  this  apparatus  as  with  those  made  with 
the  Gilmore  needles. 

Fig.  72  shows  an  arrangement  for  mounting  the  Gilmore  nee- 


Fig.  72,  Gilmore  Needles  Mounted  on  Stand. 

dies  so  that  they  always  bear  perpendicularly  and  evenly  upon  the 
top  of  the  pat. 

A  simpler  form  of  Vicat  needle  is  that  designed  by  J.  W. 
Bramwell1.  This  apparatus  is  shown  in  Fig.  73.  It  consists  of 
two  separate  rods,  each  weighing  300  grams.  One  of  these  rods 
is  fitted  with  a  cylinder,  one  cm.  in  diameter,  which  is  to  be  used 
for  determining  normal  consistency.  The  other  rod  is  provided 
with  a  needle  of  I  mm.  diameter  for  the  setting  time  test.  The 
rods  are  graduated  so  that  the  penetration  can  be  read  by  means 
of  a  pointer  on  the  lower  guide  of  the  frame.  The  upper  guide 
is  provided  with  a  thumb  screw  to  hold  the  rods  at  any  height  de- 
sired and  the  rods  themselves  all  provided  with  stops  to  prevent 
them  from  falling  and  damaging  the  needle,  etc.  Whichever  rod 
is  not  in  use  is  held  upright  by  means  of  a  peg  fitting  in  a  hole 

1  Chemical  Engineer  III,  i,  20. 


Fig.  73,  Bramwell's  Improved  Vicat  Needle. 


TIME  OF  SETTING  303 

in  the  top  of  the  rod,  as  shown  in  the  illustration.  A  glass  plate 
and  hard  rubber  ring  are  also  provided  with  this  apparatus,  as 
with  the  ordinary  Vicat  needle.  One  of  the  noteworthy  things 
about  the  Bramwell  apparatus  is  its  simplicity  and  low  price — 
about  one-half  that  of  the  standard  Vicat. 

The  "ball"  test  for  determining  the  proper  consistency  is  much 
used  in  commercial  laboratories,  using  the  Gilmore  needles  to  de- 
termine set,  and  in  spite  of  its  crudeness,  gives  results  which  agree 
fairly  well  with  those  determined  by  the  Vicat  apparatus.  It  con- 
sists in  forming  the  mortar  into  a  ball  and  dropping  it  from  a 
height  of  one  foot.  This  fall  should  not  materially  flatten  nor 
crack  the  ball,  the  former  denoting  too  much  water  in  the  mortar 
and  the  latter  not  enough. 

When  cement  sets  hard  a  few  minutes  after  the  mortar  is  mix- 
ed it  is  said  to  have  a  "flash"  set.  Some  cements  are  so  quick 
setting  that  they  even  set  up  under  the  trowel  and  on  working  get 
dryer  instead  of  more  and  more  plastic. 

OBSERVATIONS  ON  SETTING  TIME. 

The  rapidity  with  which  a  cement  sets  furnishes  us  with  no  in- 
dication of  its  strength.  The  test  is  usually  made  to  determine 
the  fitness  of  the  material  for  a  given  piece  of  work.  For  ex- 
ample, in  most  submarine  work  a  quick-setting  cement  is  desired, 
that  is,  a  cement  which  loses  its  plasticity  in  less  than  half  an 
hour,  while  for  most  purposes  where  sufficient  time  will  be  given 
the  cement  to  harden  before  being  brought  into  use,  a  slow-set- 
ting cement  will  usually  answer  better,  or  one  that  sets  in  half  an 
hour  or  more.  The  slow-setting  cements  can  be  mixed  in  larger 
quantities  than  the  quick-setting,  and  do  not  have  to  be  handled 
so  quickly,  so  that  for  most  purposes  where  permissible  they  are 
used. 

Factors  Influencing  the  Rate  of  Setting. 

The  rate  of  set  is  determined  by  a  number  of  things,  chief  of 
which  are  temperature  and  the  percentage  of  water  used  in  mak- 
ing the  mortar : — The  higher  the  temperature  the  quicker  the  set 
and  the  larger  the  percentage  of  water  the  slower  the  set.  Tern- 


304 


PORTLAND   CEMENT 


perature  has  a  very  marked  influence,  and  many  cements  which 
are  suitable  for  use  in  this  country  could  not  be  used  in  the 
tropics.  Similarly  in  the  early  spring  and  late  fall  when  the  tem- 
perature out  of  doors  is  from  20°  to  30°  F.  below  that  indoors, 
cement  which  tests  up  quick  in  the  laboratory  may  give  perfect 
satisfaction  when  used  at  the  outside  temperature.  This  influ- 
ence is  shown  by  the  results  given  below : 

TABLE  XXVTL— INFLUENCE  OF  TEMPERATURE  ON  THE  RATE  OF  SET- 
TING OF  PORTLAND  CEMENT. 


Temp. 

Sample  No. 

i 

2 

3                                4 

H. 

M. 

H. 

M 

H. 

M.             H. 

! 

1C, 

u»-     - 

Initial  set 

O 

5 

o 

2 

0 

2 

10 

,..35 

Final  set 

8 

O 

10+ 

6 

0 

6 

o 

45 

Initial  set 
Final  set 

i 

3 

5 

15 

3 

7 

O 

30 

I 
3 

15 

3° 

I 
3 

5 

15 

60 

Initial  set 
Final  set 

0 

i 

30 

10 

2 

6 

30 

0 

o 

i 

o    1       o 

3 

10 

8 

Initial  set 

o 

4 

2 

oo 

o 

2 

Final  set 

o 

10 

5 

30 

o 

5 

100 

Initial  set 
Final  set 

•• 

•• 

o 

3 

45 

10 

•  • 

•• 

-• 

The  percentage  of  water  used  to  gauge  the  pats,  or  in  actual 
work  to  make  the  mortar,  effects  the  setting  time,  as  well  as  the 
early  strength  of  the  concrete,  very  greatly.  A  wet  mixture  sets 
very  slowly,  while  a  dry  one  sets  much  more  promptly.  In  the 
manufacture  of  hollow  building  blocks,  where  the  piece  must  be 
removed  from  the  molds  at  once,  only  as  small  a  quantity  of 
water  as  is  actually  needed  to  do  the  work  is  used,  and  the  mix- 
ture of  about  the  consistency  of  damp  sand  is  rammed  into  the 
molds;  while  in  some  forms  of  concrete  construction,  the  mor- 
tar is  made,  decidedly  plastic,  and  may  be  actually  poured  into  the 
forms.  It  is  then  left  several  days  to  harden  before  the  latter  are 
removed.  Below  are  given  some  results  on  the  effects  of  various 
percentages  of  water  on  the  setting  time  of  Portland  cement : 

1  Of  room  during  setting  time  and  of  cement  and  of  water  used  to  gauge  pats. 


TIME  OF  SETTING 


305 


TABLE     XXVIII.— INFLUENCE  OF  VARIOUS    PERCENTAGES  OF   WATER 

USED  TO  GAUGE  THE  PATS  ON  THE  SETTING  TIME  OF 

PORTLAND  CEMENTS. 


Per- 
cent- 
age of 
water. 

Sample  No. 

i 

2 

3 

4 

H. 

M. 

H. 

M. 

H. 

M. 

H. 

M. 

Initial  set 

0 

10 

2 

IO 

O 

IO 

O 

25 

• 

Final  set 

2 

45 

6 

O 

O 

35 

O 

55 

16 

Initial  set 

0 

20 

2 

20 

O 

IO 

0 

25 

Final  set 

3 

50 

6 

o 

O 

35 

I 

0 

18 

Initial  set 

i 

5 

2 

20 

O 

10 

35 

Final  set 

5 

o 

6 

15 

0 

35 

I 

15 

20 

Initial  set 

2 

10 

2 

40 

O 

8 

I 

25 

Final  set 

6 

20 

6 

15 

0 

30 

4 

o 

22 

Initial  set 

4 

20 

3 

0 

0 

5 

2 

15 

Final  set 

8 

0 

6 

50 

0 

30 

5 

o 

24 

Initial  set 

5 

10 

5 

o 

0 

20 

3 

o 

••? 

Final  set 

12  + 

8 

30 

0 

50 

6 

JO 

Rise  in  Temperature  During  Setting. 

It  was  formerly  the  practice  to  determine  the  rise  in  tempera- 
ture during  setting,  any  considerable  increase  being  considered  as 
indicative  of  free  lime  in  the  cement,  the  supposition  being  that 
the  rise  is  caused  by  the  heat  formed  by  the  hydration  of  the  lime. 
No  conclusion  could  be  more  erroneous.  From  the  examination 
of  many  samples  of  Portland  cement,  every  detail  of  whose  manu- 
facture was  known,  I  am  not  afraid  to  say  positively,  that  the  rise 
of  temperature  during  setting  is  not  only  indicative  of  free 
lime,  but  usually  conies  from  the  reverse,  not  enough  lime.  Those 
cements  which  show  the  greatest  increase  in  temperature  during 
the  process  of  setting  are  usually  the  quick  setting  cements.  These 
cements  usually  are  low  in  lime  and  burned  very  hard.  Many 
samples  of  such  cements  show  a  rise  of  temperature  distinctly  per- 
ceptable  to  the  hand,  and  yet  boiling  for  many  hours  will  fail  to 
disintegrate  the  pat  or  warp  or  check  it  in  any  manner.  In  many 
instances,  the  addition  of  a  small  quantity  (^  per  cent.)  of  finely 
ground  lime  or  i  or  2  per  cent,  of  slaked  lime  will  slow  the  set- 


3O6  PORTLAND   CEMENT 

ting  of  the  cement,  and  in  this  case  no  rise  of  temperature  will  be 
met  with,  showing  that  the  presence  of  free  lime  is  not  the  cause 
of  the  rise  in  temperature  during  setting.  On  the  other  hand  many 
samples  which  fail  badly  after  even  a  few  hours  of  the  steam  test, 
show  no  greater  rise  in  temperature  than  the  normal.  When  there 
is  a  considerable  rise  in  temperature  during  the  setting  of  a  slow 
setting  cement,  something  is  probably  wrong  with  the  cement,  but 
when  the  rise  is  met  with,  in  connection  with  quick  set,  it  is  no 
evidence  of  free  lime,  and  the  conclusion  that  it  is,  is  unwarranted 
by  facts. 

Influence  of  Sulphates  on  Setting  Properties. 

If  Portland  cement  clinker  is  ground  just  as  it  comes  from  the 
coolers,  without  the  addition  of  any  foreign  substance,  the  re- 
sulting cement  is  entirely  too  quick  setting  to  allow  of  its  being 
properly  worked.  It  is  therefore  the  general  practice  to  either 
grind  a  small  percentage,  usually  2  or  3  per  cent.,  of  gypsum  with 
the  clinker  or  else  to  add  to  the  cement  just  before  it  is  shipped, 
a  corresponding  percentage  of  finely  ground  plaster  of  Paris,  in 
order  to  regulate  the  set  so  as  to  give  time  for  working,  tamping 
and  troweling.  At  some  mills  coarsely  ground  plaster  of  Paris, 
or  calcined  plaster  as  the  manufacturers  call  it,  is  added  to  the 
clinker  before  grinding. 

Le  Chatelier  made  many  experiments  on  the  effect  of  the  addi- 
tion of  gypsum  and  plaster  of  Paris  to  Portland  cement.  He  con- 
cluded that  the  governing  action  which  it  exercised  over  the  ce- 
ment was  due  to  the  formation  of  certain  soluble  compounds  be- 
tween the  sulphuric  acid  of  the  calcium  sulphate  and  the  very  ac- 
tive calcium  aluminates  of  the  cement  which  cause  quick  setting. 
He  also  stated  that  either  gypsum  or  plaster  of  Paris  could  be 
added  to  slow  the  set  and  that  the  addition  could  be  made  either 
before  or  after  burning.  Since,  however,  calcium  sulphate  is  de- 
composed at  temperatures  decidedly  below  that  at  which  Portland 
cement  is  burned  there  would  be  a  decided  disadvantage,  owing 
to  loss  of  SO3,  in  adding  gypsum  before  burning.  Indeed  from 
experiments  made  by  the  writer  if  all  the  sulphur  entering  the 
kiln  came  out  with  the  clinker  as  calcium  sulphate  there  would 
be  no  need  to  add  either  gypsum  or  plaster  of  Paris. 


TIME  OF  SETTING  307 

In  spite  of  Le  Chatelier's  experiments,  it  has  been  the  theory 
generally  held  in  this  country  that  gypsum  would  not  retard  the 
set  of  cement,  but  that  the  only  form  of  sulphate  of  lime  which 
would  do  this  is  plaster  of  Paris  ;  and  that  where  gypsum  is  ground 
in  with  the  clinker,  this  is  transformed  into  plaster  of  Paris,  the 
heat  generated  during  grinding  being  sufficient  to  drive  off  the 
water  and  make  the  change  from  CaSO4.2H2O  to  (CaSO4)2H2O. 
It  is  true  that  in  many  cases  the  heat  generated  by  the  friction  of 
the  grinding  machinery  is  sufficient  to  drive  off  the  water,  as  the 
writer  has  frequently  tested  cement  fresh  from  the  tube  mill  and 
found  it  over  130°  C.,  the  temperature  at  which  gypsum  loses 
three-quarters  of  its  water  of  crystallization.  Indeed  Shenstone 
and  Cundall  state  that  gypsum  begins  to  lose  its  water  of  crys- 
tallization at  70°  C.  in  dry  air. 

To  test  these  various  contrary  theories  and  statements  the 
writer  and  his  assistant,  Mr.  W.  P.  Gano,  carried  out  the  follow- 
ing experiments  i1 

A  sample  of  cement  was  prepared  by  grinding  fresh  normal 
clinker  in  the  usual  way  without  the  addition  of  any  retarder.  To 
separate  portions  of  this  were  added  in  different  percentages  fine- 
ly ground — 

(1)  Piaster  of  Paris,  (CaSO4),.H2O,  containing  53.18%  SO3. 

(2)  Gypsum  CaSO4.2H,O,  containing  44.32%  SO3. 

(3)  Dead  Burned  Gypsum,  CaSO4,  containing  55.21%  SO3. 
The  results  are  given  in  the  tables  below : 

The  first  column  shows  the  percentage  of  gypsum,  etc.,  added  to 
the  cement.  By  percentage  is  not  meant  the  percentage  of  gyp- 
sum in  the  mixture,  but  the  percentage  of  the  weight  of  cement 
of  gypsum  which  is  added.  For  instance,  2  per  cent,  means  2 
grains  of  gypsum  added  to  100  grams  of  cement,  etc. 

The  second  column  shows  the  percentage  of  water  used  for  the 
pat,  being  the  amount  necessary  to  obtain  a  mortar  of  normal  con- 
sistency, as  determined  by  the  ball  test.  The  third  column  shows 
the  "initial  set"  or  the  time  necessary  for  the  cement  to  harden 
sufficiently  to  bear  the  light  Gilmore  wire,  */i2  mch  in  diameter, 
loaded  with  y\  pound.  The  fourth  column  shows  the  "final  set'' 

i  Meade  and  Gano,  Chemical  Engineer,  I,  2,  92. 


PORTLAND   CEMENT 


or  the  time  necessary  for  the  cement  to  harden  sufficiently  to  bear 
the  heavy  Gilmore  wire,  'l/.2i  inch  in  diameter,  loaded  with  one 
pound. 

TABLE  XXIX.— SHOWING  THE  EFFECT   OF  PLASTER  OF  PARIS  ox  THE 
SETTING  TIME  OF  CEMENT. 


Percentage 
of  Plaster 
of  Paris 
added. 

Percentage  of 
water  used  to 
make  pats. 

Initial  set. 

Final  set. 

Hours. 

Minutes. 

Hours. 

Minutes. 

o 

25 

0 

2 

O 

6 

0.5 

23 

O 

5 

O 

10 

1.0 

23 

O 

50 

4 

o 

1.5 

23 

2 

5° 

6 

o 

2.0 

22 

3 

0 

6 

15 

3 

22 

i 

45 

5 

20 

4 

22 

o 

35 

4 

O 

5 

22 

o 

16 

2 

O 

10 

22 

0 

16 

I 

30 

20 

22 

0 

9 

O 

20 

TABLE  XXX. — SHOWING  THE  EFFECT  OF  GYPSUM  ON  THE  SETTING 
TIME  OF  CEMENT. 


Percentage 
of 
Gvpsum 
added. 

Percentage 
of  water 
used  to 
make  pats. 

Initial  set. 

Final  set. 

Hours. 

Minutes. 

Hours. 

Minutes. 

I 

23 

0 

2 

JO 

2 

23 

2 

40 

5 

50 

3 

22 

2 

50 

5 

50 

5 

22 

3 

15 

6 

oo 

10 

22 

3 

O 

5 

40 

20 

22 

3 

20 

6 

oo 

Referring  to  the  tables  it  will  be  seen  that  there  is  little  choice  in 
the  three  forms  of  calcium  sulphate  so  far  as  efficiency  goes,  all 
doing  the  work  of  retarding  the  set  about  equally  well.  This  is 


TIME  OF  SETTING 


309 


to  be  expected.  If  the  retardation  is  due  to  chemical  action  there 
is  no  reason  why  any  one  of  the  three  forms  should  not  be  as  effi- 
cient as  the  others,  because  they  all  have  approximately  the  same 
solubility,  that  of  I  part  in  400-500  parts  of  cold  water.  The  solu- 
tion of  any  of  the  four  would  merely  be  one  of  a  mixture  of  two 
kinds  of  ions,  CaO  and  SO3,  and  the  SO3  anions  would  be  as 
free  to  react  on  the  aluminates  of  lime  if  their  source  was  gypsum 
as  they  would  if  they  came  from  plaster  of  Paris. 

TABLE  XXXI.— SHOWING  THE  EFFECT  OF  DEAD  BURNED   GYPSUM  ON 
THE  SETTING  TIME  OF  CEMENT. 


Percentage 
of  Dead 
Burned 
Gvpsum 
added. 

Percentage 
of  water 
used  to 
make  pats. 

Initial  set. 

Final  set. 

Hours. 

Minutes. 

Hours. 

Minutes. 

I 

23 

O 

6 

0 

10 

2 

23 

I 

45 

5 

10 

3 

23 

I 

47 

5 

30 

5 

23 

2 

o 

5 

40 

10 

23 

I 

50 

5 

O 

20 

23 

2 

20 

5 

o 

It  will  be  noticed,  by  reference  to  Table  XXIX,  that  2%  plaster 
of  Paris  produced  the  maximum  retardation  of  the  set.  Larger 
quantities  than  this  had  the  effect  of  quickening  the  set  of  the 
cement.  This  maximum  of  course  varies  with  different  cements, 
but  with  all  it  will  be  found  that  there  is  a  point  beyond  which  ad- 
ditions of  plaster  will  be  attended  with  shortening  instead  of 
further  lengthening  the  setting  time  of  the  cement.  This  phenom- 
ena is  no  doubt  due  to  the  fact  that  plaster  of  Paris  itself  is  very 
quick  setting.  This  explanation  is  strengthened  by  the  fact  that 
the  addition  of  large  quantities  of  calcium  sulphate  in  the  other^ 
two  forms  (See  Tables  II  and  III),  neither  of  which  has  any  set- 
ting properties  of  its  own,  does  not  cause  any  quickening  of  the 
set. 

As  we  have  said  many  manufacturers  prefer  to  add  plaster  of 
Paris  to  cement  just  before  it  is  shipped.    If  it  is  properly  mixed 


3io 


PORTLAND  CEMENT 


with  the  cement  there  are  certainly  points  in  favor  of  adding  the 
sulphate  here.  We  do  not  see,  however,  why  finely  ground  gyp- 
sum would  not  do  the  work  just  as  well,  saving  the  cost  of  cal- 
cining. On  the  other  hand  if  the  gypsum  is  added  to  the  clinker, 
it  is  sure  to  be  finely  ground  and  thoroughly  disseminated 
throughout  the  cement,  two  things  necessary  with  any  form  of 
sulphate,  if  it  is  to  act  as  a  retarder.  There  will  be  no  danger  of 
the  gypsum  failing  to  do  its  work,  whether  the  temperature  is  low 
or  high  during  grinding,  because  dehydration  is  not  necessary. 
It  must  be  remembered,  however,  that  plaster  of  Paris  contains 
more  sulphuric  acid  than  gypsum,  290  parts  of  the  former  being 
equivalent  to  344  of  the  latter  or  a  ratio  of  87:100  so  that  plaster 
of  Paris  weight  for  weight  is  the  more  effective  of  the  two. 
Along  this  line,  dead  burned  gypsum  is  still  more  effective  and 
should  be  cheaper  than  plaster  calcined  by  the  kettle  process. 

Influence  of  Calcium  Chloride  on  Setting  Time. 
Another  substance  which  will  retard  the  setting  of  cement  is 
calcium  chloride,  though  the  writer  has  never  heard  of  its  being 
used  in  practice.  Candlot  made  many  experiments  upon  the  effect 
of  chloride  of  calcium  on  the  setting  time  of  ground  cement  clink- 
er. Below  are  some  of  his  results : 

TABLE  XXXII.— INFLUENCE  OF  CALCIUM  CHLORIDE  ON  THE  SETTING 
TIME  OF  PORTLAND  CEMENT. 


Solution  of  CaCl2 
Gr.  per  Litre. 

I 
h.  m. 

2 

h.  m. 

h.  m. 

4 
h.  m. 

2 

0.05 

1.05 

8.00 

i-34 

5 

o.oS 

10.  CO 

I2.OO 

2.OO 

10 

8.18 

10.00 

14.00 

5-50 

20 

I.OO 

12.  OO 

10.30 

8.00 

40 

4.35 

8.00 

6.30 

8.35 

60 

3.20 

6.00 

4.00 

6  oo 

100 

0.03 

0.20 

0.30 

3-30 

200 

0.03 

0.09 

0.05 

0.25 

300 

O.O2 

0.08 

0.03 

0.05 

TIME:  OF  SETTING 


311 


Carpenter1  also  made  some  experiments  on  grinding  the  clinker 
and  calcium  chloride  together.  His  results  are  given  below  and 
show  that  chloride  of  calcium  has  effect  in  retarding  the  time  of 
setting  and  exerts  the  greatest  effect  when  about  one-half  of  I 
per  cent,  by  weight  of  the  chloride  of  calcium  is  employed : 

TABUS  XXXIII.— INFLUENCE  OF  CaCl2  GROUND  DRY  WITH  THE 

CLINKER. 


Per  cent, 
of  CaCl2. 

Per  cent, 
of  water. 

Initial  set. 

Final  set. 

0.0 

29.8 

1*5 

274 

0-5 

34-1 

160 

272 

1.0 

29.8 

I67 

234 

i-5 

26.4 

127 

212 

2.0 

25.4 

103 

1  80 

2-5 

26.4 

45 

182 

3-0 

26.4 

97 

185 

3-5 

26.4 

63 

150 

4-5 

28.6 

73 

160 

5-0 

29.8 

76 

84 

5-5 

29.8 

68 

H5 

6.0 

29.8 

% 

Effect  of  Storage  of  Portland  Cement  on  Its  Setting  Properties. 

No  property  of  Portland  cement  is  harder  to  contro^  than  its 
"set,"  or  gives  the  manufacturer  more  trouble.  This  is  not  so 
much  because  of  any  difficulty  in  the  way  of  making  a  slow  set- 
ting cement,  as  it  is  of  making  one  which  will  stay  slow  setting 
under  all  ordinary  conditions  of  storage  and  aging.  Every  manu- 
facturer can  cite  instances  of  cement  which  left  the  mill  having 
the  proper  setting  time,  and  yet  which  turned  up  at  the  job  with  a 
"flash"  set.  Bins  of  freshly  made  cement  will  frequently  test  slow 
setting  and  yet,  after  seasoning  some  weeks,  will  show  quick  set 
on  again  testing. 

The  converse  of  this  is  also  true,  some  cements  which,  when 

,  Journal  of  Engineering,  (Cornell  Univ.)  January,  1905. 


312 


PORTLAND  CEMENT 


freshly  made  are  quick  setting,  will  in  time  become  slow  setting, 
and  again  slow  setting  cements  may  become  quick  setting  and 
then  slow  setting  again.  As  a  usual  rule  a  cement  which  is  slow 
setting  when  freshly  made  and  which  becomes  quick  setting  on 
storage  is  under-limed,  and  the  trouble  can  usually  be  remedied 
by  increasing  the  percentage  of  lime  in  the  cement.  High  limed, 
well  burned  and  made  cements  do  not  usually  show  this  fault. 
What  percentage  of  lime  it  is  necessary  to  carry  in  order  to 
avoid  this  trouble  is  a  question  every  mill  must  decide  for  itself, 
but,  in  general,  it  may  be  said  that  cements  high  in  alumina  will 
require  a  high  percentage  of  lime  to  overcome  this  fault,  and  in 
some  instances  the  margin  between  the  minimum  of  lime  to  insure 
against  quick  set  and  the  maximum  allowed  by  a  good  hot  test  is 
very  narrow. 

The  table  below  illustrates  the  changes  in  the  setting  time  of 
cement,  due  to  aging. 

TABLE  XXXIV.— INFLUENCE  OF  AGING  ON  THE  SET  OF  PORTLAND 

CEMENT. 


Sample  No. 

i 

2 

3 

4 

5 

6 

7 
M 

H 

M 

H 

M 

H 

M 

H 

M 

Fi 

M 

H 

M 

H 

Fresh 

Initial  set 
Final  set 

2 

6 

50 
o 

3 
6 

ro 
40 

4 

8 

10 

O 

2 

6 

40 
15 

2 
15 

• 

IO 
25 

• 

4 

10 

i  week  old  

Initial  set 
Final  set 

i 
4 

30 

10 

10 

2S 

2 

6 

15 

o 

8 

2 

IO 

5 
IS 

4 

IO 

2  weeks  old  .  .  . 

Initial  set 
Final  set 

0 
0 

3 
7 

5 
n 

i 

§ 

25 

40 

3 

8 

15 

3S 

I 

30 
OS 

4 

10 

4  weeks  old-  .  • 

Initial  set 
Final  set 

0 

0 

3 

7 

5 
15 

I 

30 

5p 

• 

5 
ii 

I 

4 

30 

IO 

I 

4 

50 
45 

• 

15 
30 

3  months  old.  . 

Initial  set 
Final  set 

I 

30 
15 

;; 

4 
15 

10 

30 

3 
8 

j 
4 

35 
o 

2 

6 

0 
10 

2 

6 

40 
5 

6  months  old.  . 

Initial  set 
Final  set 

I 

25 
15 

i° 

20 

10° 

• 

; 

3 
8 

2 

6 

IO 

o 

2 

6 

o 

IO 

2 

5 

IO 

40 

i  year  old 

Initial  set 
Final  set 

I 

25 

10 

2 

55 
30 

2 

5 

20 

45 

4 

10 

2 

5 

o 

3° 

i 
5 

40 

5 

2 

6 

'5 
o 

The  reason  commonly  given  for  the  quickening  of  the  set  of 
Portland  cement  is  that  the  plaster  of  Paris  (CaSO4)2  H2O,  has 
hydrated  and  reverted  to  gypsum, CaSO4.2H2O.  It  is  a  fact, 
however,  as  is  generally  well  known,  and  as  we  have  mentioned 
before  that  gypsum  is  practically  as  efficacious  a  retarder  as 


TIME  OF  SETTING 


313 


plaster  of  Paris.  Not  only  will  the  mineral  gypsum  slow  the  set 
of  cement  but  the  artificial  gypsum,  formed  when  plaster  hydrates 
or  sets,  will  also  act  in  the  same  manner,  as  the  following  re- 
sults will  show. 

TABLE  XXXV.— THE  EFFECT  OF  "SET"  PLASTER  OF   PARIS  ON  THE 
SETTING  TIME  OF  CEMENT. 


Percentage  of 
"Set"  Plaster  of 
Paris  added. 

Percentage  of 
Water  used  to 
make  pats. 

Initial  set. 

Final  set. 

Hours. 

Minutes. 

Hours. 

Minutes. 

0 

25 

O 

2 

0 

6 

I 

23 

O 

8 

O 

40 

2 

23 

I 

45 

5 

o 

3 

23 

2 

o 

5 

20 

5 

23 

I 

45 

6 

O 

10 

23 

I 

55 

5 

35 

20 

23 

2 

15 

5 

50 

In  view  of  the  fact  that  both  gypsum  and  set  plaster  of  Paris, 
which  is  merely  plaster  of  Paris  reverted  into  gypsum,  will  slow 
the  set  of  cement,  there  can  be  nothing  in  the  theory  that  plaster 
loses  its  control  in  time  over  cement,  for  the  only  change  which 
the  plaster  can  undergo  is  to  absorb  water  from  the  air  forming 
gypsum.  We  must  therefore  seek  for  another  solution  of  the 
matter.  Mr.  Clifford  Richardson  suggested  one,  in  his  paper  on 
the  "Constitution  of  Portland  Cement,"  read  before  the  Associa- 
tion of  Portland  Cement  Manufacturers,  at  Atlantic  City,  June, 
1904.  His  theory  being  that  the  tension  in  the  solid  solution  of 
calcium  silicates  and  aluminates,  which  constitutes  cement,  is  re- 
leased by  changes  in  temperature,  etc.,  setting  free  some  alumi- 
nate  which  makes  the  cement  quick-setting  again. 

Against  this  latter  theory  are  several  facts,  chief  of  which  is  that 
cements  kept  in  air-tight  vessels  do  not  get  quick-setting.  The 
writer  has  many  times  divided  a  sample  of  cement,  which  from  its 
analysis  led  him  to  believe  it  would  develop  a  "flash"  set  on  aging, 
into  two  portions,  storing  one  in  a  small  paper  bag  and  the  other 
in  an  air  tight  fruit  jar,  and,  in  no  case,  has  he  ever  observed  the 


314  PORTLAND   CEMENT 

sample  in  the  jar  to  become  quick-setting,  although  in  most  cases 
that  in  the  bag  developed  an  initial  set  of  from  2  to  10  minutes 
after  a  week's  time.  In  making  this  test  three  parts  were  always 
made  of  each  sample,  both  before  and  after  aging,  and  the  bag 
and  jar  were  placed  side  by  side  on  the  shelf,  where  both  would 
be  subjected  to  the  same  changes  of  temperature,  etc. 

Influence  of  Slaked  Lime  on  Setting  Time. 

Where  cement  has  become  quick  setting  from  storage  it  can 
generally  be  made  slow  setting  again  by  simply  adding  I  or  2 
per  cent,  of  slaked  lime,  or  by  gauging  the  pat  with  lime  water. 
This  seems  to  lead  to  the  conclusion  advanced  by  Candlot  that 
the  quickening  of  the  set  of  cement  on  exposure  to  air  is  due  to 
the  change  of  the  small  percentage  of  free  or  of  hydrated  lime  al- 
ways present  in  cement  to  the  inert  carbonate.  This  change  is 
brought  about  by  the  carbon  dioxide  of  the  air,  consequently, 
when  not  exposed  to  the  air,  the  cement  does  not  become  quick- 
setting.  Slaked  lime  will  not  itself  slow  the  setting  of  unsul- 
phated  cement,  and  calcium  sulphate  must  be  present  in  some 
form  or  other,,  so  that  it  is  probably  a  mixture  of  calcium  sul- 
phate and  calcium  hydrate  which  retards  the  hydration  of  the 
aluminates,  and  consequently  the  activity  of  the  cement. 

Cement  which  has  become  quick-setting  may  also  be  made  slo\t"- 
setting  again  by  addition  of  a  small  percentage  of  plaster  of  Paris. 
One-half  of  one  per  cent,  is  usually  sufficient  for  this  purpose. 
When  bins  of  cement  have  become  quick-setting,  from  age,  it  is 
usual  to  bring  the  setting  time  back  to  normal  by  such  means. 
Usually  a  square  box  made  to  hold  so  much  plaster  of  Paris 
(when  struck  off  level)  is  added  to  every  barrow  of  cement  as  it 
is  wheeled  from  the  bin  to  the  conveyor,  or  else  a  box  is  dumped 
into  the  conveyor  at  stated  intervals  of  time.  The  screw  conveyor 
then  does  the  mixing  and  usually  does  it  pretty  thoroughly,  too. 
Some  mills  are  provided  with  automatic  scales  and  mixers  for 
doing  this  work,  but  these  are  usually  installed  only  in  those  mills 
which  use  plaster  of  Paris  and  make  the  addition  before  packing, 
instead  of  grinding  gypsum  in  with  the  clinker. 

Quick-setting  cement  may  also  be  rendered  slow-setting  by  mix- 


TIME  OF  SETTING  315 

ing  them  with  slow-setting  ones,  but  this  must  be  carefully  done 
to  see  that  both  bins  are  drawn  from  in  the  desired  proportions. 

The  property  slaked-lime  has  of  slowing  the  setting  time  of  ce- 
ment which  has  quickened  with  age  does  not  seem  to  be  utilized 
as  much  as  it  might  be.  I  know  of  one  cement  mill  where  slaked 
lime  was  added  for  a  short  time  for  this  purpose  and  of  another 
which  contemplated  doing  so.  Most  manufacturers,  however, 
have  found  it  simpler  to  add  a  little  more  plaster  of  Paris  to  such 
cement  as  becomes  quick-setting,  just  before  it  is  packed  and  so 
bring  back  its  setting  time  to  the  normal.  The  contractor  or  engi- 
neer, however,  might  in  many  cases  add  slaked  lime  to  the  cement 
and  so  relieve  the  manufacturer  of  the  expense  of  taking  the  ce- 
ment back  to  the  mill  in  order  to  plaster  it.  On  small  jobs,  where 
water  is  added  to  the  concrete  from  barrels,  the  addition  of  a  few 
lumps  of  lime  to  the  contents  of  the  barrel  would  make  the  ce- 
ment slow-setting,  and  the  resulting  concrete  would  be  as  strong 
as  if  no  lime  had  been  added.  Sidewalk  makers  and  other  users 
of  cement  who  do  not  test  their  purchases  may  safeguard  them- 
selves against  using  quick-setting  cement  unawares  by  the  use  of 
lime  in  this  way. 


CHAPTER  XVI. 


TENSILE  STRENGTH. 


STANDARD  SPECIFICATION  AND  METHOD  OF  TEST 


Specification. — The  minimum  requirements  for  tensile  strength 
for  briquettes  one  inch  square  in  section  shall  be  within  the  fol- 
lowing limits,  and  shall  show  no  retrogression  in  strength  within 
the  periods  specified  :x 

Age.  Neat  Cement.  Strength. 

24  hours  in  moist  air 1 50-200  Ibs 

7  days  (i  day  in  moist  air,  6  days  in  water) 450-550  Ibs 

28  days  ( i  day  in  moist  air,  6  days  in  water) 550-650  Ibs 

One  Part  Cement,  Three  Parts  Sand. 

7  days  (i  day  in  moist  air,  6  days  in  water)  150-200  Ibs 

28  days  ( i  day  in  moist  air,  6  days  in  water) 200-300  Ibs 

Method  of  Operating  the  Test. 
Standard  Sand. 

For  the  present,  the  committee  recommends  the  natural  sand 
from  Ottawa,  111.,  screened  to  pass  a  sieve  having  20  meshes  per 
linear  inch  and  retained  on  a  sieve  having  30  meshes  per  linear 
inch;  the  wires  to  have  diameters  of  0.0165  and  0.0112  in.,  re- 
spectively, i.  e.,  half  the  width  of  the  opening  in  each  case.  Sand 
having  passed  the  No.  20  sieve  shall  be  considered  standard  when 
not  more  than  I  per  cent,  passes  a  No.  30  sieve  after  one  minute 
continuous  sifting  of  a  5OO-gram  sample. 

The  Sandusky  Portland  Cement  Company,  of  Sandusky,  Ohio, 
has  agreed  to  undertake  the  preparation  of  this  sand  and  to  fur- 
nish it  at  a  price  only  sufficient  to  cover  the  actual  cost  of  prepa- 
ration. 

1  For  example  the  minimum  requirement  for  the  twenty-four  hour  neat  cement  test 
should  be  some  value  within  the  limits  of  150  and  200  pounds,  and  so  on  for  each  period 
stated. 


TENSILE  STRENGTH 


317 


Form  of  Briquette. 

While  the  form  of  the  briquette  recommended  by  a  former  com- 
mittee of  the  Society  is  not  wholly  satisfactory,  this  committee  is 
not  prepared  to  suggest  any  change,  other  than  rounding  off  the 
corners  by  curves  of  3^  in.  radius,  Fig.  74. 

8* 


Fig.  74,  Standard  Form  of  Briquette. 

Molds. 

The  molds  should  be  made  of  brass,  bronze  or  some  equally 
non-corrodible  material,  having  sufficient  metal  in  the  sides  to 
prevent  spreading  during  molding. 

Gang  molds,  which  permit  molding  a  number  of  briquettes  at 


3l8  ,  PORTLAND   CEMENT 

one  time,  are  preferred  by  many  to  single  molds ;  since  the  greater 
quantity  of  mortar  that  can  be  mixed  tends  to  produce  greater 
uniformity  in  the  results.  The  type  shown  in  Fig.  75  is  recom- 
mended. 

The  molds  should  be  wiped  with  an  oily  cloth  before  using. 

Mixing. 

All  proportions  should  be  stated  by  weight;  the  quantity  of 
water  to  be  used  should  be  stated  as  a  percentage  of  the  dry  mate- 
rial. 

The  metric  system  is  recommended  because  of  the  convenient 
relation  of  the  gram  and  the  cubic  centimeter. 

The  temperature  of  the  room  and  the  mixing  water  should  be 
as  near  21°  C.  (70°  F.)  as  it  is  practicable  to  maintain  it. 


Fj"g-  75,  Gang  Mold,  I<ever  Clamp. 

The  sand  and  cement  should  be  thoroughly  mixed  dry.  The 
mixing  should  be  done  on  some  non-absorbing  surface,  preferably 
plate  glass.  If  the  mixing  must  be  done  on  an  absorbing  surface 
it  should  be  thoroughly  dampened  prior  to  use. 

The  quantity  of  material  to  be  mixed  at  one  time  depends  on 
the  number  of  test  pieces  to  be  made;  about  1,000  gr.  (35.28  oz.) 
makes  a  convenient  quantity  to  mix,  especially  by  hand  methods. 

Method. — The  material  is  weighed  and  placed  on  the  mixing 
table,  and  a  crater  formed  in  the  center,  into  which  the  proper  per- 
centage of  clean  water  is  poured;  the  material  on  the  outer  edge 
is  turned  into  the  crater  by  the  aid  of  a  trowel.  As  soon  as  the 
water  has  been  absorbed,  which  should  not  require  more  than  one 
minute,  the  operation  is  completed  by  vigorously  kneading  with 
the  hands  for  an  additional  il/2  minutes,  the  process  being  simi- 
lar to  that  used  in  kneading  dough.  A  sand-glass  affords  a  con- 
venient guide  for  the  time  of  kneading.  During  the  operation  of 


STRENGTH  3IQ 

mixing,  the  hands  should  be  protected  by  gloves,  preferably  of 
rubber. 

Moulding. 

Having  worked  the  paste  or  mortar  to  the  proper  consistency 
it  is  at  once  placed  in  the  molds  by  hand. 

Method. — The  molds  should  be  filled  at  once,  the  material 
pressed  in  firmly  with  the  fingers  and  smoothed  off  with  a  trowel 
without  ramming ;  the  material  should  be  heaped  up  on  the  upper 
surface  of  the  mold,  and,  in  smoothing  off,  the  trowel  should  be 
drawn  over  the  mold  in  such  a  manner  as  to  exert  a  moderate 
pressure  on  the  excess  material.  The  mold  should  be  turned  over 
and  the  operation  repeated. 

A  check  upon  the  uniformity  of  the  mixing  and  molding  is  af- 
forded by  weighing  the  briquettes  just  prior  to  immersion,  or 
upon  removal  from  the  moist  closet.  Briquettes  which  vary  in 
weight  more  than  3  per  cent,  from  the  average  should  not  be 
tested. 

Storage  of  the  Test  Pieces. 

During  the  first  24  hours  after  molding,  the  test  pieces  should 
be  kept  in  moist  air  to  prevent  them  from  drying  out. 

A  moist  closet  or  chamber  is  so  easily  devised  that  the  use  of 
the  clamp  cloth  should  be  abandoned  if  possible.  Covering  the 
test  pieces  with  a  damp  cloth  is  objectionable,  as  commonly  used, 
because  the  cloth  may  dry  out  unequally,  and  in  consequence  the 
test  pieces  are  not  all  maintained  under  the  same  conditions. 
Where  a  moist  closet  is  not  available,  a  cloth  may  be  used  and 
kept  uniformly  wet  by  immersing  the  ends  in  water.  It  should 
be  kept  from  direct  contact  with  the  test  pieces  by  means  of  a 
wire  screen  or  some  similar  arrangement. 

A  moist  closet  consists  of  a  soapstone  or  slate  box,  or  a  metal- 
lined  wooden  box — the  metal  lining  being  covered  with  felt  and 
this  felt  kept  wet.  The  bottom  of  the  box  is  so  constructed  as  to 
hold  water,  and  the  sides  are  provided  with  cleats  for  holding 
glass  shelves  on  which  to  place  the  briquettes.  Care  should  be 
taken  to  keep  the  air  in  the  closet  uniformly  moist. 

After  24  hours  in  moist  air  the  test  pieces  for  longer  periods  of 


320 


PORTLAND   CEMENT 


time  should  be  immersed  in  water  maintained  as  near  21°  Cent. 
(70°  Fahr.)  as  practicable;  they  may  be  stored  in  tanks  or  pans, 
which  should  be  of  non-corrodible  material. 

Tensile  Strength. 

The  tests  may  be  made  on  any  standard  machine.  A  solid 
metal  clip,  as  shown  in  Fig.  76,  is  recommended.  This  clip  is  to 
TABLE  XXXVI. — PERCENTAGE  OF  WATER  FOR  STANDARD  MIXTURES. 


Neat. 

i-i 

1-2 

i-3 

1-4 

i-5 

IS 

12.  0 

IO.O 

9.0 

8.4 

8.0 

19 

12.3 

IO.2 

9-2 

8-5 

8.1 

20 

12-7 

10.4 

9-3 

8.7 

8.2 

21 

13.0 

10.7 

9-5 

8.8 

8-3 

22 

13.3 

10.9 

9-7 

8-9 

8.4 

23 

13-7 

ii.  i 

9.8 

9-i 

8-5 

24 

14.0 

n-3 

IO.O 

9-2 

8.6 

25 

14-3 

n.6 

10.2 

9-3 

8.8 

26 

14.7 

11.  8 

10.3 

9-5 

8.9 

27 

15-° 

12.  0 

10.5 

9.6 

9.0 

28 

15-3 

12.2 

10.7 

9-7 

9-1 

29 

15-7 

12-5 

10.8 

99 

9-2 

30 

16.0 

12.7 

II.  0 

IO.O 

9-3 

31 

16.3 

I2.9 

II.  2 

10.  I 

9-4 

32 

16.7 

I3-I 

n-3 

10.3 

9-5 

33 

17.0 

13-3 

ii.  5 

10.4 

9-6 

34 

17-3 

13-6 

11.7 

10.5 

9-7 

35 

17-7 

13-8 

ii.  8 

10.7 

9-9 

36 

18.0 

14.0 

12.0 

10.8 

IO.O 

37 

18.3 

14.2 

12.2 

10.9 

10.  1 

38 

18.7 

14-4 

12.3 

ii.  i 

10.2 

39 

19.0 

14-7 

12-5 

II.  2 

10.3 

40 

19-3 

14.9 

12.7 

ii-3 

10.4 

4i 

19.7 

I5-I 

12.8 

ii.  5 

10.5 

42 

20.  o 

15-3 

13.0 

it  .6 

10.6 

43 

20.3 

15.6 

13.2 

11.7 

10.7 

44 

20.7 

I5.8 

13-3 

n-9 

10.8 

45 

21.0 

16.0 

13-5 

12.0 

II.  0 

46 

21-3 

16.1 

13.7 

12.  1 

ii.  i 

I  tO  I 

I  tO  2 

i  to  3 

i  to  4 

i  to  5 

Cement  •  •  •  • 

500 

333 

250 

200 

I67 

Qotirl 

coo 

666 

7^O 

800 

S^u 

y+> 

/Ow 

UOO 

be  used  without  cushioning  at  the  points  of  contact  with  the  test 
specimen.  The  bearing  at  each  point  of  contact  should  be  l/\.  in. 
wide,  and  the  distance  between  the  center  of  contact  on  the  same 
clip  should  be  ij4  ins- 


TKNSIUJ  STRENGTH 


32I 


Test  pieces  should  be  broken  as  soon  as  they  are  removed 
from  the  water.  Care  should  be  observed  in  centering  the  bri- 
quettes in  the  testing  machine,  as  cross-strains,  produced  by  im- 
proper centering,  tend  to  lower  the  breaking  strength.  The  load 
should  not  be  applied  too  suddenly,  as  it  may  produce  vibration, 
the  shock  from  which  often  breaks  the  briquette  before  the  ulti- 
mate strength  is  reached.  Care  must  be  taken  that  the  clips  and 
the  sides  of  the  briquette  be  clean  and  free  from  grains  of  sand 


Fig.  76,  Standard  Form  of  Clip. 

or  dirt,  which  would  prevent  a  good  bearing.  The  load  should  be 
applied  at  the  rate  of  600  Ibs.  per  minute.  The  average  of  the 
briquettes  of  each  sample  tested  should  be  taken  as  the  test,  ex- 
cluding any  results  which  are  manifestly  faulty. 

OTHER  METHODS. 

Standard  Sand. 

Up  to  the  adoption  of  the  above  standard  rules,  crushed  quartz 
such  as  is  used  in  the  manufacture  of  sand  paper,  was  considered 
the  standard  sand,  having  been  recommended  by  a  former  com- 

ii 


322 


PORTLAND  CEMENT 


mittee  of  the  American  Society  of  Civil  Engineers.  Indeed,  it  is 
probable  that  it  is  still  used  in  by  far  the  greater  number  of  test- 
ing laboratories  in  the  country.  As  this  sand  is  a  commercial  pro- 
duct it  can  be  obtained  in  large  quantities  and  of  standard  grades. 
The  crushed  quartz  should  be  of  such  size  that  it  will  all  pass  a 
No.  20  sieve  and  yet  be  retained  upon  a  No.  30. 

Where  the  value  of  the  cement  is  desired  with  regard  to  some 
particular  piece  of  work,  the  sand  used  for  the  test  may  be  the 
sand  that  is  to  be  used  for  the  work.  In  this  case  it  is  the  mortar 
that  is  tested  rather  than  the  cement.  Just  as  a  series  of  tests 
made  with  a  standard  sand  and  various  brands  of  cement  would 
give  the  comparative  value  of  the  cements,  so  a  series  of  tests  with 


Fig.  77,  Old  Standard 
Form  of  Briquette. 


Fig.  78,  German  Standard 
Form  of  Briquette. 


an  established  brand  of  cement  and  various  sands  will  give  the 
comparative  value  of  the  sands. 

Cement,  when  tested  with  the  natural  Ottawa  sand,  usually 
shows  a  greater  strength  than  when  tested  with  crushed  quartz. 
In  the  case  of  7  day  breaks,  the  higher  figure  may  be  as  much  as 
40  per  cent,  of  the  lower.  The  reason1  for  this  difference  is  due 
to  the  shape  of  the  sand  grains.  The  Ottawa  sand  being  round,  it 
compacts  much  more  closely  and  has  a  lower  percentage  of  voids 
than  crushed  quartz,  as  the  latter  has  sharp  and  angular  grains, 
which  mass  and  wedge,  leaving  more  space  between  the  sand  par- 
ticles. 

Forms  of  Briquettes. 

Fig.  77  shows  the  form  of  briquette  recommended  in  the  report 
of  a  former  committee  on  a  uniform  system  for  tests  of  cement 

1  Brown,  Proceedings  of  Am.  Soc.  for  Test.  Mat.,  IV.,  (1904),  124. 


TENSILE  STRENGTH  323 

of  the  American  Society  of  Civil  Engineers,1  which  is  similar  to 
the  present  standard  except  that  the  latter  has  rounded  corners. 
Fig.  78  shows  the  form  recommended  by  the  Association  of  Ger- 
man Cement  Makers,  which  is  the  standard  in  Germany.  The 
dimensions  of  the  two  forms  are  given  in  the  drawings.  As  will 
be  seen,  the  weakest  section  of  briquettes  of  either  form  is  at  the 
center  and  is  one  inch  in  cross-section,  in  the  case  of  the  United 
States  standard ;  and  5  square  centimeters  in  that  of  the  German. 
Comparative  tests  show  the  American  standard  to  give  the  higher 
result  of  the  two.  In  the  case  of  briquettes  of  neat  cement,  this 
difference  amounts  sometimes  to  as  much  as  30  or  40  per  cent,  of 
the  lower. 

The  briquettes  to  be  broken  at  the  expiration  of  twenty-four 
hours  are  made  of  neat  cement,  that  is,  cement  alone,  while  those 
to  be  broken  only  after  the  lapse  of  seven  days  or  longer,  should 
be  made  both  of  neat  cement  and  of  a  mixture  of  one  part  cement 
to  three  parts  sand. 

Molds. 

The  various  kinds  of  molds,  other  than  the  standard  form,  used 
in  this  country  for  making  briquettes,  are  shown  in  Figs.  62,  63 
and  79.  They  are  usually  made  of  gun  metal,  brass,  or  some 


Fig.  79,  Form  of  Molds. 

alloy  of  copper  that  does  not  easily  rust  on  exposure  to  moisture. 
They  are  made  in  two  pieces  to  facilitate  the  removal  of  the  bri- 
quette after  molding.  When  in  use  the  two  sections  are'  held  to- 
gether by  means  of  a  lever  clamp,  or  a  clamp  provided  with  a 
thumb-screw,  or  by  a  spring.  Preference  is  usually  to  be  given 
to  the  clamp  rather  than  to  the  spring,  as  the  latter  is  likely  to 
give  a  little  during  the  ramming  of  the  mortar  into  the  mould, 
allowing  the  mould  to  spread,  which  would  result  in  a  distorted 
briquette,  and  an  enlarged  breaking  section. 

i  This  committee  presented  its  report  at  the  annual  meeting  of  the  society,  January 
21,  1885,  and  was  then  discharged. 


324 


PORTLAND  CEMENT 


Fig.  80  shows  another  form  of  gang  mold.  If  a  hole  is  bored 
through  from  side  to  side  of  this  mould,  between  the  third  and 
fourth  openings,  so  as  not  to  interfere  with  the  briquettes,  and  a 
bolt  provided  with  a  thumb-screw  is  run  through  this  the  mould 
will  be  considerably  stiffened  thereby  and  springing  will  be 
guarded  against. 


Fig.  80,  Gang  Mold,  Screw  Clamp. 

To  clean  the  molds,  lay  them  all  flat  on  the  table  without  the 
clamps  just  as  if  briquettes  were  to  be  made  and  scrape  off  any 
hardened  cement  with  a  piece  of  sheet  zinc  or  other  soft  metal. 
Then  brush  off  with  a  stiff  bristle  brush  and  wipe  with  a  piece  of 
oily  waste.  Turn  the  molds  over  and  repeat  the  process  on  the 
other  face.  Now  separate  the  molds  and  place  the  halves  in  a  long 
line  with  the  mold  part  forming  a  trough,  brush  with  a  stiff  brush 
and  wipe  off  with  oily  waste.  Briquettes  should  not  be  allowed 
to  become  too  hard  before  removing  from  the  molds.  For  most 


Fig.  81,  Scraper  for  Cleaning  Molds. 

cements,  if  briquettes  are  made  in  the  morning,  they  can  be  re- 
moved from  the  molds  in  the  afternoon,  and  the  molds  cleaned  at 
once  before  the  cement  hardens. 

Fig.  8 1  shows  a  scraper  for  cleaning  molds.     This  consists  of 


TENSILE  STRENGTH 


325 


a  block  of  wood  5x3  inches,  rounded  to  form  a  handle,  into  which 
is  fixed  a  piece  of  zinc. 

Mixing. 

In  place  of  a  glass  plate,  a  sheet  of  brass  ^-inch  thick  makes 
an  excellent  mixing  surface.  Slate  and  soapstone  slabs  are  also 
used.  Both,  however,  absorb  water  and  draw  it  away  from  the 
briquettes.  This  can  be  avoided  by  keeping  a  damp  cloth  over 


A 


G/erss  7>/a 


S 


Waste. 
Can 


J         L 


Fig.  82,  Table  for  Mixing  Mortar  and  Making  Briquettes  and  Pats. 

that  part  of  the  table  used  for  mixing  when  not  in  service.  Or 
melted  paraffin  may  be  poured  over  the  heated  slab  and  allowed 
to  soak  in  and  the  whole  then  cooled.  The  excess  of  paraffin  is, 
of  course,  to  be  scraped  off  with  a  metal  scraper. 

Fig.  82  shows  a  convenient  table  for  mixing  mortar  and  mak- 
ing briquettes  and  pats.  It  consists  of  a  table  arranged  with  glass 
or  brass  plates  or  slate  slabs  at  either  end  and  the  central  part  of 
the  table  raised  four  or  five  inches  above  the  ends  as  shown.  The 
space  between  the  shelf  and  the  glass  plate  is  left  open  so  that  the 
surplus  mortar,  etc.,  used  in  making  a  set  of  briquettes  may  be 


326 


PORTLAND  CEMENT 


swept  through  this  and  into  a  waste-can  placed  below.  A  piece 
of  tin  bent  to  form  a  trough,  as  shown,  conducts  the  waste  into 
the  can.  Above  the  first  shelf,  which  is  used  for  the  scales,  meas- 
uring cylinders,  pat  glasses,  etc.,  a  second  shelf  is  supported  by 
four  uprights — one  at  each  corner.  At  each  end  of  this  shelf  are 
to  be  placed  2-gallon  bottles  provided  with  siphons  of  glass  and 
rubber,  as  shown.  These  siphons  are  closed  by  pinch-cocks,  as 
shown.  Drawers  may  be  placed  in  the  front  of  the  table  for  hold- 
ing such  articles  as  trowels,  spatulas,  etc.  Four  2-gallon  bottles 
should  be  provided,  and  while  two  are  in  use  on  the  table  the 
other  two  should  be  full  and  standing  nearby  to  get  the  room 
temperature. 

Instead  of  kneading  the  cement  mortar  with  the  hands  as  pre- 
scribed by  the  standard  rules,  the  larger  number  of  testers  use  a 
trowel,  working  the  mortar  back  and  forth  on  the  table,under  the 
trowel. 

Percentage  of  Water. 

The  percentage  of  water  used  in  gauging  the  mortar  for  the 
test  pieces  has  a  considerable  influence  on  the  strength  of  the 
cement.  This  is  shown  by  the  table  given  below  which  is  taken. 

TABLE  XXXVII. — INFLUENCE  OF  VARIOUS  PROPORTIONS  OF  WATER  ON 
THE  NEAT  STRENGTH  OF  PORTLAND  CEMENT.    (E.  S.  LARNED). 


Tensile  Strength. 

Brand. 

Per  cent. 

Hours. 

Days. 

Days. 

Months. 

Months. 

Months. 

15 

371 

655 

875 

941 

720 

787 

16 

3°3 

750 

973 

1008 

735 

816 

Giant 

18 

260 

649 

773 

831 

645 

748 

Portland. 

20 

233 

500 

693 

7l6 

621 

676 

22 

184 

546 

636 

658 

601 

589 

24 

167 

539 

649 

644 

629 

755 

13 

366 

775 

859 

1067 

892 

832 

U 

404 

780 

891 

972 

852 

781 

Atlas 
Portland. 

16 

18 

20 

363 
308 
225 

602 
570 
590 

725 
723 
718 

844 
7g5 
760 

806 
728 
674 

723 
724 
636 

22 

116 

554 

649 

731 

643 

604 

24 

42 

5io 

691 

695 

632 

574 

TENSILE  STRENGTH  327 

from  a  paper  by  Mr.  E.  S.  Larned1  on  this  subject.  It  will  be 
noticed  that  in  the  case  of  both  cements,  the  dryer  mixtures  give 
the  higher  results.  This  is  probably  due  to  the  fact  that  the  dry 
mixtures  require  hammering  or  ramming  to  get  them  in  the 
molds,  while  the  wet  mixtures  were  merely  forced  in  with  the 
thumb  as  they  were  too  soft  for  this  treatment.  Other  experi- 
menters, however,  have  found  results  differing  in  some  particu- 
lars from  Mr.  Larned,  and  while  agreeing  with  him  that  the 
dryer  mixtures  give  higher  short  time  tests,  their  experiments 
show  the  differences  on  long  time  tests  to  be  slight  and  usually 
in  favor  of  the  wet  mixtures.  This  has  also  been  the  writer's 
experience,  but  in  his  case  both  the  dry  and  the  wet  mixtures 
were  merely  pressed  into  the  molds  with  the  thumbs. 

Storage   of   Briquettes. 

The  briquettes  may  be  placed  in  water  either  flat  or  on  edge. 
The  latter  gives  more  surface  exposed  to  the  water.  The  tanks 
in  which  the  briquettes  are  immersed  may  be  made  of  galvanized 
iron  and  of  any  desired  size.  They  are  usually,  however,  from 
two  to  three  inches  deep.  Where  space  is  limited,  they  may  be 
placed  one  above  the  other  on  a  suitable  framework. 

When  much  testing  has  to  be  done,  a  good  form  of  trough  for 
the  storage  of  briquettes  is  made  of  stout  two-inch  board  lined 
with  sheet  zinc.  These  troughs  may  be  placed  one  above  the 
other  on  a  suitable  wood  frame.  A  small  stream  of  water 
should  be  kept  running  through  them  all  the  time.  This  can  be 
done  by  arranging  overflow  tubes  so  that  the  water  will  flow 
from  the  upper  trough  into  the  next  one  below,  etc. 

In  the  writer's  laboratory,  the  briquette  trough  is  placed  in 
the  cellar  and  is  made  of  concrete.  It  is  raised  about  2  feet  from 
the  floor  and  is  8  inches  deep.  The  water  level  is  maintained  at 
about  6  inches.  The  temperature  of  this  cellar  is  very  even  both 
in  summer  and  winter.  In  making  the  trough,  a  very  dense  con- 
crete was  used  so  as  to  be  sure  of  no  leakage  from  it  into  the 
cellar. 

After  the  briquettes  have  attained  their  initial  set  they  should 
be  marked  with  an  identifying  number  by  a  steel  die  and  dated 

i  Proceedings,  Amer.  Soc.  Test.  Mat.,  III.,  (1903),  401. 


328  PORTLAND   CEMENT 

as  shown  in  Fig.  83.  The  marking  should  always  be  done  in  the 
corners  and  never  across  the  breaking 'section.  Sand  briquettes 
may  be  marked  by  putting  a  thin  layer  of  neat  cement  about 
Vie  inch  thick  on  one  end  and  marking  this.  The  usual  plan, 
however,  is  only-  to  mark  the  neat  briquettes  and  store  the  sand 
briquettes  with  these,  in  the  trough,  in  such  a  manner  as  to  make 
identification  possible.  When  briquettes  are  only  to  be  made  for 
short  periods  a  pencil  may  be  used  for  marking,  but  where  long 
time  tests  are  made  steel  dies  should  be  used. 

In  storing  the  briquettes  in  the  troughs,  it  will  be  found  most 
convenient  to  put  all  the  briquettes  to  be  broken  in  7  days,  in 
order  of  making,  in  one  part  of  the  trough,  and  those  for  28 
days  in  another,  etc.  The  briquettes  may  be  placed  edgewise, 


Fig.  83,  Marked  Briquette. 

in  pairs,  one  on  top  the  other;  and  where  the  sand  briquettes 
are  not  marked,  it  will  be  found  a  good  plan  to  place  the  neat 
briquettes  over  the  corresponding  sand  ones. 

The  number  of  briquettes  to  be  made,  and  the  time  when  these 
are  to  be  broken,  will  vary  with  circumstances.  Usually,  in  per- 
manent laboratories,  briquettes  are  made  to  be  broken  at  periods 
of  24  hours,  7  days,  28  days,  3  months,  6  months,  i  year,  2  years, 
5  years  and  10  years.  Usually  from  3  to  5  briquettes,  both  sand 
and  neat,  are  broken  at  each  period,  except  at  24  hours,  when  only 
neat  briquettes  are  broken.  In  temporary  laboratories,  however, 
the  long  time  tests  are,  of  course,  omitted.  Three  neat  and  three 
sand  briquettes  are  usually  considerd  enough  to  test  the  strength 
of  cement  at  any  period,  though  in  some  laboratories  only  two  of 
each  kind  are  broken. 


TENSILE  STRENGTH 


329 


The  briquettes  should  always  be  put  in  the  testing  machine  and 
broken  immediately  after  being  taken  out  of  the  water,  and  the 
temperature  of  the  briquette  and  of  the  testing  room  should  be 
constant,  between  60°  and  70°  F.  Seven  days  neat  briquettes  kept 
in  the  room  and  allowed  to  dry  out  for  24  hours  before  breaking, 
in  many  instances,  break  at  less  than  half  the  strain  of  those  kept 
in  water  the  full  period.  Sand  briquettes,  however,  seldom  show 
any  very  marked  difference. 

Testing  Machines. 

The  Fairbanks  cement  testing  machine  is  much  used  for  cement 
testing  because  of  its  simplicity  and  automatic  action.  It  is 
shown  in  Fig.  84.  It  consists  of  a  cast  iron  frame  A,  made  in 


Fig  84,  Fairbank's  Automatic  Cement  Testing  Machine. 

one  piece  with  a  shot  hopper  B.  To  this  frame  are  hung  the  two 
levers  D  and  C.  From  the  end  of  the  upper  lever  the  weight  is 
applied  by  allowing  shot  to  flow  from  the  hopper  into  the  bucket 
F.  The  tension  is  applied  to  the  briquettes  held  in  the  clips  N 
and  N  by  means  of  the  lower  lever  C.  The  lower  clip  is  attached, 
by  means  of  a  ball  joint,  to  a  screw  with  a  hand  wheel,  for  lower- 
ing or  raising,  when  putting  in  the  briquette  and  taking  up  the 
slack.  There  is  also  a  counterbalance  E,  for  bringing  the  levers 


33O  PORTLAND  CEMENT 

and  bucket  into  partial  equilibrium  so  that  the  final  adjustment 
can  be  made  with  the  ball  L.  The  shot  hopper  is  provided  with  a 
lever  and  gate  J,  which  cuts  off  the  shot  as  soon  as  the  specimen 
breaks.  The  shot  is  weighed  by  hanging  the  bucket  on  the  oppo- 
site end  of  the  lever  D,  by  means  of  a  sliding  poise  R. 

To  operate  the  machine : 

Hang  the  cup  F  on  the  end  of  the  beam  D  as  shown  in  the 
illustration.  See  that  the  poise  R  is  at  the  zero  mark,  and  balance 
the  beam  by  turning  the  ball  L. 

Fill  the  hopper  B  with  fine  shot,  place  the  specimen  in  the 
clamps  N  N,  and  adjust  the  hand  wheel  P  so  that  the  graduated 
beam  D  will  rise  to  the  stop  K.  Open  the  automatic  valve  J  so 
as  to  allow  the  shot  to  run  slowly  into  cup  F.  When  the  specimen 
breaks,  the  graduated  beam  D  will  drop  and  automatically  close 
the  valve  J. 

If  the  elasticity  of  the  cement  is  such  that  the  specimen  will 
not  break  before  the  beam  strikes  the  valve,  it  will  be  necessary 
to  stop  the  flow  of  shot  and  readjust  the  hand  wheel.  This  can 
best  be  done  by  lifting  the  end  of  the  beam  against  the  stop  by 
hand  and  tightening  the  hand  wheel  to  hold  the  beam  firmly  in 
position.  The  shot  is  then  allowed  to  run  until  the  specimen 
breaks. 

Remove  the  cup  with  the  shot  in  it,  and  hang  the  counterpoise 
weight  G  in  its  place. 

Hang  the  cup  F  on  the  hook  under  the  large  ball  E,  and  pro- 
ceed to  -weigh  the  shot  in  the  regular  way,  using  the  poise  R  on 
the  graduated  beam  D,  and  the  weights  H  on  the  counterpoise 
weight  G. 

The  result  will  show  the  number  of  pounds  required  to  break 
the  specimen. 

The  flow  of  shot  can  be  regulated  by  the  cut-off  valve. 

In  breaking  a  specimen  in  the  above  form  of  the  Fairbanks 
machine,  it  is  necessary  to  screw  the  clips  up  tight  before  allowing 
the  shot  to  run  into  the  bucket,  in  order  to  guard  against 
having  to  do  this  later  on  in  the  breaking.  This  "initial  load" 
which  with  neat  briquettes  may  amount  to  at  least  400  Ibs.,  has 
been  given  as  one  of  the  chief  objections  to  this  machine.  The 


TENSILE  STRENGTH 


331 


manufacturers,  however,  have  placed  on  the  market  a  new 
machine  in  which  the  hand  wheel  is  replaced  by  a  gear,  which  is 
actuated  by  a  worm,  which  in  turn  is  moved  by  a  crank  in  front 
of  the  machine.  This  does  away  with  the  initial  strain. 

The  Riehle  machine  (Fig.  85)  has  all  the  weight  upon  one 
long  graduated  beam.  The  load  is  applied  to  the  briquette  by 
means  of  the  lower  hand  wheel  which  actuates  a  worm  gear, 
while  the  beam  is  kept  in  balance  by  a  weight  which  is  moved 


Fig.  85,  Riehl6  Cement  Testing  Machine. 

along  the  beam  on  a  carriage  by  the  upper  hand  wheel.  The  upper 
lever  serves  as  an  indicator.  In  testing  a  briquette  both  wheels 
must  be  moved  simultaneously  so  that  the  indicator  vibrates  in  the 
center  of  the  gate.  In  testing  w7ith  this  machine,  the  briquette 
is  placed  in  the  grips,  and,  being  carefully  adjusted,  the  hand 
wheel  connected  to  the  lower  grip,  is  turned  from  left  to  right, 
and  continued  until  the  indicator  of  weighing  beam  (which  moves 
in  a  gate  at  the  top  of  the  machine  and  nearly  on  a  line  with  the 


332  PORTLAND  CEMENT 

eye  of  the  operator)  drops.  This  indicator  moves  the  reverse  of 
the  weighing  beam,  and  when  too  much  strain  is  exerted  it  falls, 
and  when  too  much  weight  is  applied  it  raises  to  the  top  of  the 
gate.  It  is  important  that  the  indicator  should  vibrate  in  the  cen- 
ter of  the  gate,  and  rest  neither  up  nor  down.  -This  result  can  be 
attained  by  carefully  manipulating  the  large  hand  wheel  and  the 
simultaneous  movement  of  the  poise  on  the  weighing  beam. 
When  the  indicating  beam  drops  down,  when  the  test  first  begins, 
the  rest  of  the  test  can  usually  continue  without  again  moving  the 
large  hand  wheel,  which  is  shown  underneath  the  end  of  the  shelf. 
As  is  readily  understood,  the  operator  propels  the  poises  back- 
ward and  forward  by  means  of  the  hand  wheel  (at  butt  end  of 
weighing  beam)  'and  cord  passing  around  a  pulley  at  the  other 
end  of  the  machine.  By  a  little  practice  a  person  gets  very  ex- 
pert, and  can  make  a  test  with  facility. 

Whichever  machine  is  used  the  load  is  to  be  applied  at  the 
rate  of  400  pounds  per  minute. 

Neither  of  these  machines  is  free  from  sources  or  error.  In  the 
Fairbanks  machine  there  is  an  error  due  to  the  fact  some  time  (in 
which  shot  is  falling  into  the  bucket)  is  taken  by  the  beam  to  fall 
to  the  valve  checking  the  shot  stream ;  even  then,  there  is  a  stream 
of  shot  extending  from  the  valve  opening  to  the  surface  of  the 
shot  in  the  bucket  which  must  fall  into  the  latter  -and  be  weighed 
as  part  of  the  load  which  broke  the  specimen,  though  this  shot  was 
not  in  the  bucket  when  the  specimen  broke.  In  the  Riehle  type  of 
machine,  there  is  an  error  due  to- the  fact  that  the  chain  is  at- 
tached to  the  poise  at  a  point  not  on  a  line  with  the  knife  edges 
of  the  beam,  giving  the  poise  a  tendency  to  lift  up  or  pull  down. 

To  avoid  the  initial  strain  to  which  a  briquette  broken  on  the 
Fairbanks,  or  other  automatic  testing  machines  of  this  type,  is 
subjected,  the  Olsen  Automatic  Cement  Testing  Machine  was 
designed.  In  this  machine  the  initial  load  is  avoided  by  an  ingen- 
ious arrangement  consisting  in  balancing  a  bucket  of  shot  against 
a  weight,  and  then  applying  the  load  by  allowing  the  shot  to  run 
out  of  the  bucket.  Fig.  86  shows  the  machine. 

Referring  to  the  cut,  it  will  be  seen  that  the  load  is  applied 
through  a  system  of  levers  by  means  of  the  weight  shown  on  the 


TENSILE   STRENGTH  333 

extreme  right.  Before  starting  a  test  this  weight  is  counter-bal- 
anced by  shot  held  in  the  kettle.  To  make  the  test  the  valve  in  the 
bottom  of  this  kettle  is  opened,  and  as  the  shot  escapes,  its  equiva- 
lent of  the  weight  on  the  right-hand  end  of  the  beam  acts  on  the 
briquette.  At  the  instant  the  briquette  breaks  the  escaping  stream 
of  shot  is  cut  off  by  the  closing  of  the  valve  in  the  bottom  of  the 


Fig.  86,  Olsen  Automatic  Cement  Testing  Machine. 

kettle,  by  the  upper  grip  striking  the  horizontal  arm  which  ex- 
tends just  above  it,  and  thus  releasing  the  curved  arm  carried  on 
the  spindle  immediately  to  the  left ;  this  curved  arm  in  turn  strik- 
ing the  valve  and  closing  it.  The  briquette  having  broken,  it  only 
remains  to  weigh  the  amount  of  shot  that  has  escaped  from  the 
pan  and  multiply  it  by  the  proper  factor  to  give  the  load  per 


334  PORTLAND   CEMENT 

square  inch  to  which  the  briquette  has  been  subjected.  The 
machine  is  furnished  with  a  spring  balance  on  which  is  placed  the 
pan  into  which  the  shot  falls.  The  dial  of  this  spring  balance  is 
graduated  so  as  to  read  in  terms  of  pounds  to  the  square  inch  on 
the  specimen.  It  follows  that  as  the  test  proceeds,  the  operator 
can  watch  the  application  of  the  load,  and  knows  at  any  instant 
exactly  what  load  is  on  the  briquette.  When  the  briquette  breaks, 
the  load  which  broke  it  is  read  at  a  glance,  and  jotted  down  with- 
out further  manipulation  or  calculation. 

Mr.  Arthur  N.  Johnson,  highway  engineer  of  the  Maryland 
Geological  Survey,  has  devised  a  novel  and  ingenious  cement  test- 
ing machine1  which  he  thus  describes : 

"The  apparatus  consists  of  three  parts,  a  cylinder,  A,  with  a 
movable  piston '  and  filled  with  water  or  some  other  liquid ;  a 
cylinder,  B,  with  elastic  sides  which  is  connected  with  the  cylinder 
carrying  the  piston,  and  a  pressure  gauge,  C,  connected  with  the 
other  two  cylinders.  The  piston  which  moves  in  the  cylinder, 
A,  is  attached  to  a  threaded  rod  working  through  a  nut  at  the  top 
of  the  cylinder ;  thus  the  motion  of  the  piston  can  be  regulated  to 
a  nicety.  When  the  piston  descends,  the  pressure  developed 
within  the  apparatus  is  registered  by  the  gauge.  The  pres- 
sure forces  the  water  into  the  middle  cylinder,  tending  to  swell 
the  elastic  portion  of  it,  at  B,  which  is  an  India  rubber  tube. 

"If  a  ring  of  any  material  is  slipped  over  the  cylinder,  B,  so 
that  the  rubber  sides  are  confined,  a  pressure  will  be  exerted 
against  the  inner  side  of  the  ring,  when  the  piston  in  the  cylinder, 
A,  is  pushed  down,  which  will  be  registered  in  pounds  per  square 
inch  by  the  gauge.  For  testing  cement,  cylindrical  rings  of  rec- 
tangular section  are  made.  These  rings,  one  of  which  is  in  posi- 
tion at  R,  are  put  over  the  center  cylinder,  after  which  a  bell- 
shaped  cap,  D,  is  placed  upon  the  test  ring  and  is  held  in  place  by 
a  nut,  E,which  is  screwed  lightly  against  the  cap.  If  this  nut  were 
not  used  the  rubber  tube  in  expanding  would  tend  to  raise  the  cap 
and  the  rubber  would  be  forced  between  the  cap  and  the  cement 
ring,  which  would  result  in  bursting  the  rubber  tube.  When  a 
cement  ring  has  been  put  in  place  the  piston  is  screwed  down  by 

1  Engineering  Record,  (1903),  XI, VIII.  20,  602 


TENSILE  STRENGTH 


335 


means  of  a  handle,  F.  This  causes  the  rubber  tube  to  swell,  push- 
ing it  against  the  inner  side  of  the  cement  ring.  A  uniform  pres- 
sure is  thus  secured  over  the  entire  inner  surface  of  the  cement 
ring,  and,  up  to  the  moment  of  rupture,  every  section  of  the  ring 
is  under  exactly  the  same  stress,  assuming  that  the  walls  of  the 
rings  are  everywhere  of  equal  thickness.  It  is  also  evident  that  all 
rings  of  the  same  size  are  subjected  to  exactly  the  same  conditions 
so  far  as  the  application  of  the  pressure  is  concerned,  and  the  dif- 


Fig.  87,  Johnson's  Cement  Testing  Machine. 

ference  in  the  pressures  at  which  different  rings  are  ruptured 
must  be  occasioned  by  a  corresponding  difference  in  the  strength 
of  the  rings.  In  other  words  the  apparatus  treats  every  test  speci- 
men exactly  alike,  not  subjecting  one  to  different  stresses  from 


PORTLAND   CEMENT 

another  as  is  the  case  with  the  usual  method  of  making  tensile 
tests  of  cement.  It  is  also  practically  impossible  for  any  shock  to 
be  given  to  the  specimen  while  under  stress  on  account  of  the  air 
which  is  enclosed  within  the  apparatus  acting  as  a  cushion. 

"So  far  experiments  have  been  carried  on  with  rings  made  in 
two  ways,  cutting  them  with  a  diamond  drill  from  a  solid  slab  of 
cement  mortar  which  has  set  the  proper  time  and  also  by  moulding 
in  moulds.  Both  methods  are  successful  with  neat  cement,  but 
mortars  composed  of  sand  and  cement  could  not  be  successfully 
drilled  with  the  style  of  drills  at  hand.  •  Another  feature  noticed 
in  connection  with  drilling  cement  rings  was  the  lack  of  uniform- 
ity in  the  size  of  the  rings,  so  that  it  was  necessary  to  measure 
each  section  in  order  to  determine  the  results.  No  such  difficulty, 
however,  has  been  experienced  in  moulding  rings.  In  order  to 
have  them  fit  in  the  testing  machine  it  will  sometimes  be  necessary 
to  grind  the  ends  of  the  rings  so  that  they  will  present  flat  sur- 
faces. It  is  very  easy  to  do  this  and  the  amount  or  grinding  re- 
quired seldom  takes  over  one  or  two  minutes.  .This  precaution 
is  necessary  to  prevent  the  rubber  tube  from  blowing  out  between 
the  test  specimen  and  the  brass  caps  which  inclose  it." 

To  do  away  with  the  personal  equation  in  the  breaking  of  the 
briquette,  Prof.  J.  M.  Porter,  Professor  of  Civil  Engineering  in 
Lafayette  College,  has  designed  an  ingenious  form  of  cement- 
testing  machine.  In  breaking  a  briquette  with  this  machine,  the 
attention  of  the  operator  is  not  required  after  the  proper  adjust- 
ment of  the  test-piece  in  the  clips.  He  describes  his  machine  as 
follows  :x 

The  load  is  applied  by  water  flowing  into  a  tank  suspended 
from  the  long  arm  of  a  very  sensitive  15  to  i  lever.  The  weight 
of  the  lever  and  tank  is  counterbalanced  by  an  adjustable  weight 
on  the  left.  Water  is  admitted  to  the  tank  from  a  large  reser- 
voir on  the  roof  under  a  practically  constant  head  of  90  feet,  so 
there  is  no  sensible  variation  of  pressure  in  the  stream  admitted 
through  a  carefully  fitted  gate  valve  in  the  supply  pipe.  The  posi- 
tion of  this  valve  at  "on,"  "off,"  and  all  intermediate  points  is 
shown  by  an  index  attached  to  the  stem  of  the  valve  and  register- 

1  Engineering  .\rzvs,  March  7,  1895. 


TENSILE   STRENGTH  337 

ing  on  a  dial  marked  off  with  the  number  of  pounds  per  minute 
applied  to  the  specimen  as  determined  and  verified  by  previous  ex- 
periment. 

When  the  briquettes  break,  the  lever  drops  a  few  inches,  then 
the  plunger  at  the  right  end  of  the  lever  enters  the  pneumatic 
stop,  and  the  lever  and  tank  are  gradually  brought  to  rest.  Dur- 
ing the  fall  of  the  tank  and  before  it  comes  to  rest,  a  chain  at- 
tached to  the  end  of  the  valve  stem  in  the  tank  is  brought  into 
tension  and  arrests  the  descent  of  the  valve  before  its  seat  stops 
descending.  The  opening  of  this  valve  allows  the  contents  of  the 
tank  to  be  quickly  discharged  into  a  hopper  placed  upon  the  floor, 
and  is  then  carried  off  through  a  waste  pipe,  to  the  sewer.  As 
soon  as  the  tank  has  discharged  its  contents,  the  weight  on  the 
left  end  of  the  lever  brings  the  lever  and  tank  into  the  position, 
the  valve  taking  its  seat  during  this  movement  and  the  machine 
is  ready  for  another  break.  The  actual  load  can  be  applied  at 
from  o  to  80  pounds  per  minute,  thus  giving  an  increase  of  stress 
of,  from  o  to  1,200  pounds  per  minute.  The  speed  generally  used 
is  400  pounds  per  minute,  and  with  the  valve  set  for  this  speed 
the  needle  beam  will  float  every  time  within  Y-,  second  of  the 
proper  time. 

The  stress  on  the  specimen  is  measured  by  a  poise  traveling  on 
a  graduated  scale  beam,  which  can  be  read  by  means  of  a  vernier 
to  i  pound  and  can  be  moved  automatically  or  by  hand  at  the 
wish  of  the  operator.  The  automatic  movement  is  accomplished 
by  the  following  described  device : 

The  horizontal  disk  and  its  engaged  friction  wheel  are  driven 
continuously  by  the  pulley  placed  at  the  lower  end  of  the  verti- 
cal shaft  and  belted  to  overhead  shafting.  This  friction  wheel  is 
feathered  to  a  sleeve  that  runs  loose  on.  its  shaft  and  carries  a 
coned  clutch  that  is  nominally  disengaged  from  its  cone,  which 
is  also  feathered  to  the  shaft,  and  can  be  moved  slightly  longi- 
tudinally on  the  shaft  into  contact  with  the  clutch  by  the  action  of 
the  vertical  lever. 

When  the  needle  beam  rises,  it  makes  contact  through  a  verti- 
cal pin  in  the  top  of  the  frame,  which  completes  an  electric  cir- 
cuit and  sends  a  current  through  the  electro-magnet  and  causes  it 


PORTLAND  CEMENT 

to  attract  its  armature  at  the  lower  end  of  the  vertical  lever, 
which,  moving  to  the  right,  engages  the  friction  clutch  and  causes 
the  shaft  to  revolve.  This  shaft  operates  the  sprocket  wheel  and 
chain,  which  draw  out  the  poise  on  the  scale  beam  until  the  needle 
beam  drops,  breaking  the  electric  circuit.  Breaking  the  electric 
circuit  releases  the  armature  and  allows  the  friction  clutch  to  dis- 
engage and  the  poise  comes  to  rest.  The  friction  wheel  may  be 
set  at  a  greater  or  less  distance  from  the  center  of  the  disk  by 
turning  the  capstan  head  nut,  and  the  chain  is  overhauled  faster 
or  slower,  causing  the  poise  to  move  accordingly.  If  desired,  the 
poise  may  be  operated  by  the  hand  wheel  without  interfering  with 
the  automatic  device  other  than  cutting  out  the  circuit.  The  chain 
is  attached  to  the  poise  in  line  with  the  three  knife-edges  of  the 
scale  beam,  hence  the  tension  in  the  chain  has  no  tendency  to  lift 
up  or  pull  down  the  poise.  This  point  is  often  overlooked  in  de- 
signing this  detail,  not  only  in  cement  machines,  but  in  testing 
machines  in  general.  The  writer  has  a  cement  machine  in  which 
the  error  due  to  this  cause  is  over  15  pounds, 

Clips. 

Some  of  the  various  forms  of  clips  are  shown  in  the  following 
illustrations.  Fig.  88  shows  that  recommended  by  the  former  corn- 


Fig.  88,  Old  Standard  Clip. 

mittee  of  the  American  Society  of  Civil  Engineers.  This  form 
does  not  seem  to  be  very  satisfactory  as  the  bearing  surface  is  in- 
sufficient and  the  briquette  is  likely  to  break  from  the  crushing 
of  its  surface  at  the  point  of  contact.  The  new  clip  Fig.  76  on  page 
321,  is  much  more  to  be  preferred.  It  affords  sufficient  bearing 
surface  without  binding.  Various  authorities  at  different  times 
have  advocated  cushioning  the  grips  by  placing  blotting  paper 
between  the  jaw  of  the  grip  and  the  briquette,  or  stretching  rubber 


TENSILE;  STRENGTH  339 

bands  around  the  jaws,  so  as  to  soften  the  point  of  contact  of 
these  with  the  test  piece.  Mr.  W.  R.  Cock1  has  devised  the  use 
of  a  rubber  bearing  as  shown  in  Fig.  89.  In  this  clip  the  line  of 
contact  between  the  grip  and  the  briquette  is  a  rubber  tube 
mounted  on  a  pin.  These  tubes  are  readily  replaced  for  a  few 
cents  when  worn  out.  Adjustable  and  roller  clips  are  also  upon 
the  market  and  seem  to  give  satisfaction.  In  order  that  the  stress 
upon  the  briquette  shall  be  along  the  proper  lines  great  care  must 
be  exercised  in  properly  centering  the  briquette  in  the  clips,  and 
the  form  of  the  latter  must  be  such  that  it  does  not  clamp  the  head 
of  the  briquette  thus  preventing  the  test  piece  from  adjusting  it- 


Fig.  89,  Rubber  Cushioned  Clip. 

self  to  an  even  bearing.  At  the  same  time  the  surface  of  contact 
must  be  sufficient  to  prevent  the  briquette  from  being  crushed  at 
this  point.  Striking  the  happy  medium  has  so  far  proved  not  any 
too  easy.  The  clips  are  usually  suspended  by  conical  bearings 
which  permit  them  to  turn  so  as  always  to  transmit  the  stress  in 
a  direct  line  btween  the  bearings. 

Lack  of  Uniformity  in  Tensile  Tests. 

In  cement  testing,  the  personal  equation  enters  very  largely 
into  the  results.  In  a  paper2  by  Prof.  James  Madison  Porter,  of 
Lafayette  College,  he  gave  a  series  of  results  upon  the  same  ce- 
ment by  nine  different  operators,  tested  by  the  method  of  the  So- 
ciety of  Civil  Engineers  as  they  understood  it.  The  results  varied 
from  75  to  247  pounds  per  square  inch.  The  first  Committee  on 
a  Uniform  System  for  Tests  of  Cement  of  the  American  Society 
of  Civil  Engineers,  in  their  report,  says : 

"The  testing  of  cement  is  not  so  simple  a  process  as  it  is  thought  to  be. 
No  small  degree  of  experience  is  necessary  before  one  can  manipulate  the 
materials  so  as  to  obtain  even  approximately  accurate  results. 

"The  first  test  of  inexperienced,  though  intelligent  and  careful  persons, 

1  Engineering  News,  Dec.  20,  1890. 
-  Engineering  News,  March  7,  1895. 


340 


PORTLAND   CEMENT 


are  usually  very  contradictory  and  inaccurate,  and  no  amount  of  experience 
can  eliminate  the  variations  introduced  by  the  personal  equations  of  the 
most  conscientious  observers.  Many  things,  apparently  of  minor  import- 
ance, exert  such  a  marked  influence  upon  the  results,  that  it  is  only  by  the 
greatest  care  in  every  particular,  aided  by  experience  and  intelligence  that 
trustworthy  tests  can  be  made." 

The  personal  equation  probably  plays  its  most  important  part 
in  the  gauging  of  the  cement,  the  making  of  the  mortar,  and  the 
molding  and  breaking  of  the  briquettes.  In  order  to  eradicate 
these  variations  of  treatment,  machines  have  been  introduced  upon 
the  market  to  do  the  work  automatically  and  so  do  away  with 
whatever  variations  the  operator  may  introduce  into  the  hand 
work,  principally  among  which  are  the  Steinbruch  and  the  Faija 
mixers  and  the  Bohine  hammer. 

Machines  for  Mi.ving  the  Mortar. 

The  Steinbruch  mixer,   (Fig.  90),  is  much  used  in  Germany 


Fig.  90,  Steinbruch  Mixer. 

and  gives  good  results;  the  chief  objection  to  its  universal  adop- 
tion in  this  country  is  its  cost,  about  $130.  It  consists  of  a  circu- 
lar shell  having  on  its  upper  side,  near  the  outer  edge  a  groove  or 
trough  in  which  the  mortar  is  mixed.  A  wheel,  whose  rim  corre- 
sponds with  the  groove  in  the  pan,  rests  in  this  trough  and  re- 


TENSILE  STRENGTH  341 

volves  around  a  fixed  horizontal  axis,  which  is  above  and  nor- 
mal to  the  axis  of  the  pan.  The  pan  is  now  made  to  revolve  about 
its  vertical  axis,  and  at  the  same  time  the  wheel  is  made  to  re- 
volve about  its  horizontal  axis,  along  with  the  pan  and  at  the 
same  rate  of  speed,  by  means  of  gearing.  The  mortar  is  thus 
rubbed  between  the  outer  rim  of  the  wheel  and  the  inner  surface 
of  the  trough.  Small  plows  scrape  the  mortar  from  the  sides  of 
the  trough,  as  the  latter  revolves,  thus  keeping  the  mortar  in  the 
bottom  of  the  trough  and  under  the  wheel.  When  the  mixing  is 
complete,  which  according  to  the  German  rules  requires  two  and 
one-half  minutes,  the  wheel  and  plows,  the  axes  of  which  are 
hinged,  are  lifted  from  the  trough  and  the  mortar  taken  out.  The 
apparatus  appears  unnecessarily  complicated,  and  its  seems  as  if 
a  simpler  and  less  expensive  form  might  be  devised  and  used  to 
advantage.  , 

The  Faija  mixer  is  the  design  of  the  late  Henry  Faija,  of  Eng- 
land.    Fig.  91  shows  the  mixer  as  made  by  Riehle  Bros.  Testing 


Fig.  91,  Faija  Mixer. 

Machine  Co.,  of  Philadelphia.  It  consists  of  a  circular  pan  of 
about  one  foot  in  diameter,  within  which  revolve  the  arms  of  a 
stirrer.  These  arms  revolve  around  their  own  axis  in  one  direc- 
tion and  around  the  pan  in  the  reverse  direction.  This  motion  is 
given  them  by  a  fixed  internally  toothed  wheel  which  actuates  the 
pinion  of  the  stirring  spindle.  To  operate,  first  find  by  means  of 
a  trial  test  by  hand  gauging  the  proper  proportion  of  water  to  ce- 


342 


PORTLAND  CEMENT 


ment.  Next  place  in  the  mixer  sufficient  cement  to  fill  a  gang 
of  molds  and  add  at  once  the  proper  quantity  of  water  for  this 
weight  of  cement.  Then  turn  the  handle  of  the  machine  fairly 
quickly  for  from  a  half  to  three-quarters  of  a  minute,  when  it 
will  be  found  that  the  cement  and  water  are  thoroughly  mixed 
and  ready  for  the  molds.  In  gauging  cement  and  sand  in  this 
machine,  first  mix  the  cement  and  sand  dry  and  then  add  the 
water,  etc. 

Machines  for  Molding  the  Briquettes. 
The  Bohme  hammer  consists  of  a  tilt  hammer  with  automatic 


Fig.  92,  Bohme  Hammer. 

action.  The  hammer  is  thus  described  by  Max  Gary  i1  "The 
hammer  is  driven  by  a  cam  wheel  of  ten  cams  actuated  by  simple 
gearing.  The  wrought-iron  handle  of  the  hammer  is  let  into  the 

1  Trans.  Am.  Soc.  C.  E.,  30,  i. 


TENSILE:  STRENGTH 


343 


cross-head  which  carries  the  axle  of  the  hammer  and  keyed  to 
this  cross-head  and  to  the  cap  so  that  it  may  be  replaced  if  worn. 
The  steel  hammer  weighing  4^  pounds,  is  similarly  fastened  to 
the  cap.  As  soon  as  the  intended  number  of  blows  has  been  de- 
livered, the  mechanism  is  automatically  checked,  the  proper  set- 
ting having  been  made  for  this  purpose  before  beginning  the 
work."  (The  number  of  blows  required  in  the  German  Standard 
test  is  150). 

"The  forms  to  receive  the  mortar  consist  of  a  lower  and  upper 
case  held  together  by  springs.     The  lower  case  for  compression 


Hig.  9?,  Jameson  Briquette  Machine  Elevation. 

specimens  consists  of  two  angle  irons  held  on  a  planed  plate  by  a 
grinding  strip  and  a  screw  acting  on  the  latter.  Upward  motion  is 
prevented  by  two  wedge-shaped  surfaces.  The  lower  case  and  half 
the  upper  one  is  filled  with  the  mortar  to  be  tested  and  a  plate  laid 
upon  its  surface.  On  this  plate  the  blows  are  delivered.  It  is 
of  vital  importance  that  the  apparatus  rests  upon  a  firm  non-elas- 
tic foundation;  preferably  it  should  be  placed  and  fastened  on  a 
pier  of  masonry." 

Prof.  Charles  D.  Jameson  describes,  in  his  book  on  Portland 
cement,  a  form  of  machine  in  use  in  his  laboratory  at  the  Univer- 
sity of  Iowa.  The  main  portion  of  the  machine  consists  of  a  cyl- 
inder (Figs.  93  and  94)  which  -is  flanged  at  the  lower  end,  this 
flange  corresponding  in  shape  and  size  to  the  upper  part  of  the 


344 


PORTLAND   CEMENT 


base.  The  cylinder  is  bolted  to  the  base  by  four  bolts,  each  bolt 
provided  with  a  filler  that  holds  the  lower  face  of  the  cylinder  i 
inch  above  the  base  plate.  Both  of  these  faces  are  accurately 
planed.  It  is  between  these  two  planed  faces  that  the  molding 
plate  swings,  the  fillers  on  the  bolts  acting  as  stops.  The  cylinder 
is  made  in  two  parts,  bolted  together.  The  bore  is  the  size  and 
shape  of  the  briquette.  In  this  bore  works  a  solid  plunger  of  the 
shape  of  the  bore.  The  length  of  the  plunger  is  sufficient  to  cover 
the  feed  hole  when  at  its  lowest  point.  The  plunger  is  connected 
to  the  lever  by  the  connecting  rod.  The  molding  plate  swings 
in  such  a  manner  that  when  at  either  extreme,  one  of  the 
openings  is  directly  beneath  the  bore  of  the  cylinder,  while  the 
other  is  directlv  over  the  extractor.  These  extractors  are  of  the 


Fig-  94.  Jameson  Briquette  Machine,  Plan. 

shape  of  the  opening  in  the  molding  plate  are  are  raised  by  levers. 
When  the  extractor  is  at  its  lowest  point  its  top  is  a  little  below 
is  to  force  the  briquette  from  the  mold.  On  the  outside  of  the 
cylinder  is  the  hopper. 

The  method  of  operation  is  as  follows :  The  piston  is  raised 
until  it  is  above  the  feed  hole,  and  the  cement  or  mortar  in  the 
hopper  is  forced  into  the  cylinder.  The  molding  plate  is  pushed 
against  one  of  the  stops  so  as  to  bring  one  of  the  openings  under 
the  cylinder  bore.  The  lever  is  forced  down  causing  the  plunger 
to  force  the  cement  or  mortar  into  the  opening  in  the  molding 
plate.  The  molding  plate  is  then  swung  against  the  other  stoj,. 
the  lower  side  of  the  molding  plate.  The  object  of  the  extractors 
This  movement  cuts  off  the  briquette  and  places  it  directly  over 


TENSILE   STRENGTH  345 

the  extractor.  The  other  opening  in  the  molding  plate  is  directly 
under  the  cylinder  bore.  The  extractor  is  raised  by  its  lever,  and 
the  briquette  forced  out  and  removed.  The  extractor  is  lowered, 
the  main  plunger  forced  down  again,  the  molding  plate  swung 
and  another  briquette  made.  The  cylinder  holds  sufficient  motar 
for  three  briquettes.  It  should  then  be  filled  again.  In  the  ma- 
chine as  described  there  is  no  way  of  regulating  the  amount  of 
pressure.  Experiments  made  by  Prof.  Jameson,  however,  indi- 
cate that  there  is  no  necessity  of  this,  probably  from  the  fact  that 
the  actual  pressure  is  so  great  under  all  circumstances  that  the 
actual  variation  forms  but  a  small  percentage  of  it,  not  sufficient 
to  vary  the  results. 

Aiken's  Method  of  Making  Briquettes. 

Mr.  W.  A.  Aiken1,  inspector  of  materials,  New  York  Rapid 
Transit  Co.,  proposes  the  following  method  for  minimizing  the 
personal  equation  in  the  mixing  and  moulding  of  briquettes : 

"The  gang  moulds  are  filled  with  dry  cement  in  three  layers, 
the  lower  two  being  tamped  by  three  blows  of  a  wooden  mallet 
and  a  tamping  iron  exactly  fitting  the  moulds,  the  top  layer  being 
simply  put  into  place,  pressed  in  and  smoothed  off  with  a  small 
trowel,  after  the  moulds  have  been  filled.  Three  blows  of  the 
mallet  were  adopted  because  repeated  experiments  demonstrated 
that  this  number  gave  results,  when  the  briquettes  were  broken, 
approximating  the  strength  desired  in  what  was  considered  the 
most  acceptable  cement  at  the  7-day  period ;  fewer  blows  not  giv- 
ing such  satisfactory  results  in  every  way,  more  blows  developing 
abnormal  strength  at  that  period  as  well  as  at  later  stages. 

"After  the  briquettes  are  finished,  as  far  as  filling  the  moulds 
is  concerned,  the  whole  is  put  into  storage  tanks  and  there  left  to 
take  up  as  much  water  as  required.  At  the  expiration  of  24  hours, 
all  the  briquettes  are  ready  to  be  taken  from  the  moulds,  when 
those  for  the  first  period  are  immediately  broken  and  the  others 
stored  in  tanks.  By  careful  weighing  of  a  great  many  sets  of 
briquettes  it  has  been  ascertained  that  22  per  cent,  of  water  by 
weight  is  taken  up  during  the  first  immersion." 

1  Proceedings  Amer.  Soc.  for  Test.  Mat.,  1904. 


346 


PORTLAND  CEMENT 


OBSERVATIONS. 

High  Tensile  Strength  of  Unsound  Cements. 

Perhaps  the  results  of  no  test  are  given  so  prominent  a  place  in 
the  manufacturers'  advertisement  as  the  neat  strength  of  bri- 
quettes made  of  his  brand.  We  hear  the  question  constantly  pro- 
pounded by  the  prospective  purchaser  of  "How  much  does  your 
cement  pull?"  and  a  thousand-pound  neat  7-day  break  is  consid- 
ered compensation  for  all  the  deleterious  qualities  a  cement  may 
have.  In  reality,  the  neat  break  is  not  of  so  much  value  as  we  are 
apt  to  suppose,  and  taken  by  itself  is  little  criterion  of  the  quality 
of  cement.  Unsound  cements  often  give  notoriously  high  results, 
and  the  addition  of  plaster  or  gypsum  will  also  increase  the  neat 
strength.  In  both  of  these  instances  there  is  apt  to  be  on  long 
time  breaks  a  falling  off  in  strength,  permanent  in  the  former  case 
and  usually  only  temporary  in  the  latter  case. 

This  is  illustrated  by  the  following  table  taken  from  a  paper  by 
Mr.  W.  P.  Taylor,  on  "Soundness  Tests  of  Portland  Cement,"1 
read  in  1903.  This  table  was  compiled  from  over  200  nearly  con- 
secutive tests  of  a  single  brand,  100  of  them  failing  in  the  test  and 
100  passing. 

TABLE  XXXVIII.— COMPARISON  OF  THE  TENSILE  STRENGTH  OF 
BRIQUETTES  PASSING  AND  FAILING  IN  THE  BOILING  TEST. 


Age. 

Failing. 

Passing. 

Neat. 

i  :  3 
Sand. 

Neat. 

Sand. 

530 
8l7 

749 
7i3 
702 

I97 

273 
274 
242 

391 
643 
727 
732 
749 

237 
303 
312 
3H 

28  Days  

It  will  be  noticed  that  the  early  strength  of  the  neat  tests  of 
those  samples  failing  to  pass  the  test  is  much  the  greater,  while 
the  opposite  is  true  of  the  sand  samples. 

1  Proceedings  Amer.  Soc.  Test.  Mat.,  III.  (1903),  381. 


TENSILE  STRENGTH  347 

Effect  of  Grinding  on  Neat  and  Sand  Strength. 

A  fact  that  is  generally  known  is  that  up  to  a  certain  point 
coarse  grinding  of  the  cement  will  give  higher  neat  results  than 
fine  grinding.  A  cement  75  per  cent,  of  which  passed  a  2OO-mesh 
sieve  gave  after  7  days  a  neat  strength  of  912  pounds  and  a  sand 
strength  of  256  pounds.  The  finer  portions  of  this  cement,  that 
passing  a  2OO-mesh  sieve,  gave  for  the  same  period  a  neat  strength 
of  715  pounds  and  a  sand  strength  of  463  pounds.  A  sample  of 
float  (i.  e.,  the  fine  cement  dust  which  collects  on  the  beams,  etc., 
in  a  cement  mill  and  which  is  nearly  all  of  it  an  impalpable  pow- 
der) gave  for  7  days  a  neat  strength  of  679  pounds  and  a  sand 
strength  of  558  pounds.  This  dust  mixed  with  25  per  cent,  of 
coarse  cement,  i.  e.,  that  passing  a  loo-mesh  screen  but  retained 
on  a  2OO-mesh,  gave  919  pounds  neat,  but  only  252  pounds  sand 
strength  in  7  days.  Certainly  in  both  these  cases  neat  strength 
would  have  given  us  a  poor  comparison  of  the  value  of  the  two 
products.  As  cement  is  always  used  with  sand,  the  sand  strength 
is  the  important  thing. 

That  the  sand  strength  and  neat  tests  do  not  necessarily  bear 
any  relation  to  each  other,  the  Table  XXXIX  will  show.  The 
sand  strength  seems  to  depend  largely  upon  the  fineness,  yet  dif- 
ferent brands  of  cement  giving  similar  residues  on  the  test  sieves 
will  not  necessarily  show  the  same  relation  between  neat  and  sand 
test.  This  latter  may,  of  course,  be  due  to  differences  in  the 
amount  of  flour,  which  is  not  shown  by  the  sieve  test,  as  well  as 
to  peculiarities  of  composition,  physical  structure,  etc.,  of  the 
clinker  from  which  the  cement  is  ground. 

Drop  in  Tensile  Strength. 

Another  point  which  has  often  been  brought  against  cement, 
and  American  cements  in  particular,  is  that  of  a  permanent  drop 
in  tensile  strength  after  the  28-day  test.  In  fairly  quick  setting 
cements  with  their  usual  low  lime  content  and  to  which  the  nor- 
mal amount  of  gypsum  or  plaster  has  been  added,  this  drop  is 
rarely  met  with  and  is  probably  then  due  to  improper  manipulation 
of  the  test.  In  cements  high  in  lime,  without  being  necessarily 
unsound,  or  in  cements  to  which  a  large  addition  of  plaster  or 


348 


PORTLAND  CEMENT 


gypsum  has  been  made,  this  drop  is  often  met  with.     In  unsound 
cements  it  is  usually  met  with,  often  after  the  7-day  test. 

It  does  not  necessarily  follow  that  any  drop  in  strength  indi- 
cates a  disrupting  action,  because  as  cement  briquettes  get  older 
they  get  more  and  more  brittle,  and  consequently  tensile  stresses 
break  them  more  easily.  Particularly  is  this  true  if  the  clips  exert 
any  twisting  action  and  the  load  is  not  very  evenly  applied.  Also 
cement  is  never  used  neat  and  in  the  vast  majority  of  cases  when 

TABLE.  XXXIX— SHOWING  LACK    OF  ANY  RELATION  BETWEEN 
NEAT  AND  SAND  STRENGTH  AND  FINENESS. 


Cement 
No. 

Boiling 
Test. 

Fineness. 

Tensile  strength, 
7  days. 

Tensile  strength, 
28  days. 

Through 
No.  100. 

Through 
No.  200. 

Neat. 

i  =3- 

Neat. 

i  =3- 

I 

O.  K. 

99.0 

80.0 

915 

303 

1013 

353 

2 

O.  K. 

99.0 

80.0 

790 

285 

853 

320 

3 

0.  K. 

99.1 

85-1 

933 

298 

990 

340 

4 

0.  K. 

98.8 

83.3 

930 

288 

963 

330 

5 

0.  K. 

94.8 

78.8 

733 

270 

825 

360 

6 

0.  K. 

95-0 

79.0 

748 

280 

620 

275 

7 

0.  K. 

96.5 

74.0 

818 

275 

858 

360 

8 

O.  K. 

97.0 

74.0 

800 

260 

1013 

280 

9 

O.  K. 

95-1 

70.0 

910 

190 

1038 

266 

10 

O.  K. 

95-0 

70.0 

683 

1  80 

750 

320 

ii 

0.  K. 

98.0 

82.5 

1008 

200 

IH5 

282 

12 

0.  K. 

97-9 

82.5 

855 

283 

970 

333 

!3 

0.  K. 

94.8 

75-0 

610 

350 

810 

440 

14 

O.  K. 

92.0 

70.0 

544 

206 

884 

261 

15 

O.  K. 

93-4 

70.4 

701 

217 

893 

3*o 

16 

O.  K. 

93-8 

74.2 

680 

359 

791 

410 

17 

0.  K. 

97.1 

82.5 

855 

283 

970 

333 

18 

0.  K. 

97-4 

82.7 

910 

255 

970 

305 

a  cement  shows  a  slight  falling  off  in  neat  strength,  the  sand 
strength  increases  with  age.  This  is  shown  in  Table  XL.  Hum- 
phreys states  that  the  compressive  strength  of  neat  cement  does 
not  experience  this  drop  when  the  cement  is  sound  even  if  the 
tensile  strength  does  fall  off  somewhat  after  the  28-day  test ;  an 
important  fact,  if  true,  as  cement  is  seldom  if  ever  used  in  ten- 
sion. 

Coarse  grinding  of  the  cement  has  some  influence  on  the  in- 
crease in  strength  with  age.     A  very  fine  cement  increases  neat 


TENSILE  STRENGTH 


349 


very  little  after  7  days,  while  a  coarser  one  keeps  on  increasing. 
This  is  no  doubt  due  to  the  fact  that  the  coarse  particles  are  acted 
on  much  slower  than  the  fine  ones,  and  solution  and  crystalliza- 
tion of  these  go  on  after  the  finer  ones  are  all  hydrated.  The  fol- 

TABLE  XL.— SHOWING  LOSS  IN  STRENGTH  OF  NEAT  BRIQUETTES 
AND  GAIN  IN  SAND  BRIQUETTES  AFTER  SEVEN  DAY  TEST. 


0 

Tensile  strength. 

c 
u 

Boiling 
Test. 

Neat. 

i  :  3  Sand. 

1 

C 

O 

7  days 

28  days 

3  mos 

6  mos 

i  year 

7  days 

28  days 

3  mos 

6  mos 

i  year 

I 

0.  K. 

657 

615 

650 

680 

711 

240 

302 

360 

381 

405 

2 

O.  K. 

9*5 

845 

73° 

76o 

755 

3IO 

360 

375 

378 

415 

3 

0.  K. 

1058 

1023 

890 

852 

783 

200 

263 

425 

4IO 

463 

4 

O.  K. 

865 

727 

730 

650 

728 

317 

353 

39° 

4OO 

416 

5 

O.  K. 

708 

656 

66  1 

663 

665 

201 

279 

402 

455 

520 

6 

O.  K. 

735 

704 

684 

688 

658 

290 

401 

426 

443 

477 

7 

O.  K. 

916 

845 

816 

825 

802 

30  [ 

'360 

424 

450 

456 

8 

O.  K. 

1012 

875 

890 

921 

944 

306 

374 

381 

410 

467 

9 

0.  K. 

912 

815 

826 

814 

827 

292 

327 

368 

381 

381 

10 

0.  K. 

856 

803 

810 

814 

811 

275 

369 

391 

418 

ii 

checked 

1150 

775 

610 

615 

674 

235 

315 

366 

381 

427 

12 

947 

816 

702 

310 

Dis. 

210 

246 

247 

311 

312 

13 

812 

304 

318 

301 

204 

294 

316 

321 

33° 

327 

14 

955 

811 

816 

802 

503 

274 

321 

375 

416 

427 

15 

927 

802 

765 

612 

344 

213 

227 

264 

375 

414 

16 

610 

3*4 

191 

78 

95 

224 

237 

241 

256 

281 

17 

I  IIO 

765 

342 

Dis. 

Dis. 

275 

298 

315 

362 

396 

lowing  experiment  was  made  with  the  same  cement.  Cement  A 
is  just  as  it  comes  from  the  mills.  Cement  B  is  cement  A  with  the 
coarse  particles  (residue  on  a  No.  200  sieve,  removed)  : 


Age. 

7  days. 

28  days. 

3  mos. 

6  mos. 

9  mos. 

Cement  A    Ibs  

6r8 

fine 

fiTc 

Cement  B   Ibs 

CTQ 

"95 

~Af. 

"75 

725 

75° 

5IS 

54° 

535 

510 

549 

Of  76  samples  of  the  same  brand  of  cement,  each  one  contain- 
ing from  63.25  to  63.75  Per  cent,  lime  when  freshly  ground  and 
passing  the  boiling  test,  those  ground  to  a  fineness  of  80-85  'per 
cent,  through  a  No.  200  sieve  showed  an  increase  of  only  3.4  per 
cent,  neat  strength  between  the  periods  of  7  and  28  days;  while 


350  PORTLAND   CEMENT 

those  ground  to  a  fineness  of  70-75  per  cent,  through  a  No.  200 
sieve  gained  18.3  per  cent,  in  this  time.  When  a  cement  gives  a 
high  neat  break  on  7  days,  and  passes  the  steam  test  when  re- 
ceived, failure  to  show  an  increase  in  28  days  should  not  be  taken 
as  an  indication  of  a  poor  cement  nor  should  the  cement  be  re- 
jected because  of  this.  Indeed,  if  the  sand  test  shows  an  increase 
in  strength  in  the  28-day  break,  the  cement  should  be  promptly 
accepted. 


CHAPTER  XVIL 


SOUNDNESS. 


STANDARD  SPECIFICATION  AND  METHOD  OF  TEST. 

Pats  of  neat  cement  about  three  inches  in  diameter,  one-half 
inch  thick  at  the  center,  and  tapering  to  a  thin  edge,  shall  be  kept 
in  moist  air  for  a  period  of  twenty-four  hours. 

(a)  A  pat  is  then  kept  in  air  at  normal  temperature  and  ob- 
served at  intervals  for  at  least  28  days. 

(b)  Another  pat  is  kept  in  water  maintained  as  near  70°  F.  as 
practicable,  and  observed  at  intervals  for  at  least  28  days. 

(c)  A  third  pat  is  exposed  in  any  convenient  way  in  an  atmos- 
phere of  steam,  above  boiling  water,  in  a  loosely  closed  vessel  for 
five  hours. 

These  pats,  to  satisfactorily  pass  the  requirements,  shall  remain 
firm  and  hard  and  show  no  signs  of  distortion,  checking,  cracking 
or  disintegrating. 

OTHER  METHODS. 

Faija's  Test. 

Probably  the  mildest  of  the  hot  tests  is  that  of  the  English  ce- 
ment expert,  Henry  Faija.  His  method  consists  in  subjecting  a 
freshly  gauged  pat  upon  a  plate  of  glass  prepared  as  directed 
above  to  a  moist  heat  of  100°  to  105°  F.  for  six  or  seven  hours, 
or  until  thoroughly  set,  and  then  immersing  it  in  water  kept  at  a 
temperature  of  115°  to  120°  F.  for  the  remainder  of  the  twenty- 
four  hours.  This  treatment  imparts  an  artificial  age  to  the  cement 
and  quickly  brings  out  any  vicious  qualities  the  cement  may  pos- 
sess. For  this  test  he  uses  the  apparatus  shown  in  Fig.  95.  It 
consists  of  a  covered  vessel  in  which  water  is  kept  at  the  even 
temperature  of  115°  to  120°  F.  by  means  of  a  water-jacket.  The 
inner  vessel  is  filled  with  water  to  the  height  shown.  Above  the 
water-level  is  placed  a  rack.  When  the  water  in  the  inner  vessel 
is  at  the  temperature  of  115°  to  120°  F.  the  upper  part  of  the  ves- 


352 


PORTLAND  CEMENT 


sel  will  be  filled  with  aqueous  vapor  and  this  latter  will  be  at  a 
temperature  of  from  100°  to  105°  F.  As  soon  as  the  pat  is 
gauged  it  is  put  on  the  rack  and  left  there  for  six  hours.  It  is 
then  placed  in  the  warm  water  and  allowed  to  remain  eighteen 
hours  longer.  The  author  of  the  test  states  that  if  a  test  pat  after 
the  above  treatment  shows  no  signs  of  cracking  or  blowing  and 
adheres  firmly  to  the  glass  plate  on  which  it  was  made,  it  may  be 
used  with  perfect  confidence ;  it  will  never  blow.  This  test  cer- 
tainly seems  fairer  to  the  cement  than  most  of  the  hot  tests,  many 


Fig.  95,  Faija's  Soundness  Test  Apparatus. 

of  which  would,  if  applied  to  some  really  good  cements,  cause 
them  to  be  rejected. 

Maclay's  Test. 

Captain  W.  W.  Maclay  modifies  this  test  as  follows:  Four 
pats  are  prepared  in  the  usual  manner.  One  of  these  pats  is 
placed  in  a  steam-bath  of  a  temperature  of  195°  to  200°  F.  as 
soon  as  made.  The  second  pat  is  placed  in  the  same  bath  as  soon 


SOUNDNESS  353 

as  it  will  bear  the  one  pound  wire.  The  third  pat  is  placed  in  the 
steam-bath  after  double  the  interval  has  passed  that  took  the  sec- 
ond pat  to  set  hard,  counting  from  the  time  of  gauging.  The 
fourth  pat  is  placed  in  the  steam-bath  after  twenty-four  hours. 
The  four  pats  are  kept  in  the  steam-bath  three  hours,  when  they 
are  immersed  in  water  at  200°  F.  for  twenty-one  hours  each, 
when  they  are  taken  out  and  examined.  All  four  pats  after  being 
twenty-one  hours  in  hot  water,  should,  to  pass  the  test  perfectly, 
upon  examination,  show  no  swelling,  cracks  nor  distortions,  and 
should  adhere  to  the  glass  plates.  This  latter  requirement,  while 
it  obtains  with  some  cements  nearly  free  from  uncombined  lime, 
is  not  insisted  upon,  the  cracking,  swelling,  and  distortion  being 
the  more  important  features  of  the  test.  Where  the  cement  is 
very  objectionable  from  excess  of  free  lime  the  trouble  generally 
shows  itself  in  the  cracking  or  distortion  of  all  four  pats.  Where 
the  cement  is  not  so  bad,  the  cracking  and  swelling  takes  place  on 
the  first  three  pats  only.  With  less  objectionable  cement  only  the 
first  two  pats  crack  or  swell  while  the  cracking  and  swelling  of 
the  first  pat  can  generally  be  disregarded. 

Captain  Maclay  does  not  consider  this  test  final,  however,  but 
where  the  cement  fails  to  pass,  gives  it  another  chance  by  testing 
briquettes  conserved  in  hot  water  and  comparing  with  those  kept 
in  cold  water.  He  found,  in  a  general  way,  that  the  average  ten- 
sile strength  of  hot  water  briquettes  of  pure  cement  four  days  old 
are  nearly  as  high  as  the  normal  seven-day  cold,  while  the  hot 
water  seven-day  briquettes  require  nearly  the  same  strain  to  pull 
them  apart  as  the  normal  twenty-eight  day  cold,  when  the  cement 
is  of  good  quality.  In  a  poor  cement,  however,  one  in  which  the 
pats  show  distortion  and  cracking,  there  is  generally  a  marked 
falling  off  of  the  hot  water  briquettes  from  the  above  comparison, 
and  one  system  can  be  used  to  check  the  other.  The  briquettes 
are  prepared  at  the  same  time  the  regular  cold  water  test-pieces 
are  made — four  additional  sets  of  five  each  for  neat  cement  and 
four  additional  sets  of  mortar.  These  are  allowed  to  set  twenty- 
one  hours  in  moist  air  of  about  60°  F.  They  are  placed  three 
hours  in  the  steam-bath  at  195°  F.  and  then  immersed  in  hot 
water  (200°  F.),  after  which  they  are  broken  when  two,  three, 

12 


354  PORTLAND  CEMENT 

four,  and  seven  days  old,  respectively,  and  the  breakings  com- 
pared with  the  normal  breakings  of  briquettes  seven  and  twenty- 
eight  days  old  kept  in  cold  water.  A  more  rational  test  would  be 
a  modification  of  the  Maclay  test  using  sand  briquettes  instead 
of  neat  ones. 

Kiln  Test. 

Dr.  Bohme  suggested  the  kiln  test.  The  Association  of  German 
Cement  Makers  recommended  this  test  as  a  means  of  quickly 
judging  of  the  quality  of  a  cement,  but  do  not  make  the  test  de- 
cisive and  abide  by  their  twenty-eight-day  test  on  those  cements 
which  fail  to  pass  the  kiln  test.  Their  method  for  the  test  is  as 
follows : 

"For  making  the  heat  test,  a  stiff  paste  of  neat  cement  and 
water  is  made,  and  from  this  cakes  8  cm.  to  10  cm.  in  diameter 
and  i  cm.  thick  are  formed  on  a  smooth  impermeable  plate  cov- 
ered with  blotting  paper.  Two  of  these  cakes  which  are  to  be 
protected  against  drying  in  order  to  prevent  drying  cracks,  are 
placed  after  the  lapse  of  twenty-four  hours,  or  at  least  only  after 
they  have  set,  with  their  smooth  surface  on  a  metal  plate  and  ex- 
posed for  at  least  one  hour  to  a  temperature  of  from  110°  C.  to 
120°  C.  until  no  more  water  escapes.  For  this  purpose  the  drying 
closets  in  use  in  chemical  laboratories1  may  be  utilized.  If  after 
this  treatment  the  cakes  show  no  edge  cracks,  the  cement  is  to  be 
considered  in  general  of  constant  volume.  If  such  cracks  do  ap- 
pear the  cement  is  not  to  be  condemned,  but  the  results  of  the 
decisive  test  with  the  cakes  hardening  on  glass  plates  under  water 
must  be  wraited  for.  It  must,  however,  be  noticed  that  the  heat 
test  does  not  admit  of  a  final  conclusion  of  the  constancy  of  vol- 
ume of  those  cements  which  contain  more  than  3  per  cent,  of  cal- 
cium sulphate  (gypsum)  or  other  sulphur  combinations." 

Prof.  Tetmajer,  of  Zurich,  modifies  this  method  by  placing  on 
the  bottom  of  the  oven  a  few  millimeters' of  water.  The  heat  is 
gradually  applied  so  as  to  evaporate  all  the  water  in  from  three  to 
six  hours;  first  that  on  the  floor  of  the  oven,  and  then  that  ab- 
sorbed by  the  mortar.  The  latter  is  held  on  a  shelf  above  the 
floor.  The  temperature  of  the  oven  remains  at  about  95°  C.  until 
the  water  is  entirely  evaporated.  After  this  the  heating  is  contin- 

1  See  page  218. 


SOUNDNESS  355 

tied  half  an  hour  longer  in  such  a  manner  as  to  raise  the  tempera- 
ture of  the  oven  to  120°  C.  This  will  bring  the  temperature  of 
the  interior  of  the  briquette  at  a  little  over  100°  C.  It  is  difficult 
to  obtain  comparative  results  by  this  method  as  the  heat  is  not 
the  same  for  all  specimens,  since  after  the  evaporation  of  the 
water,  the  heat  is  much  greater  at  the  bottom  than  at  the  top  of 
the  oven. 

Boiling  Test. 

This  test,  also  devised  by  Prof.  Tetmajer,  is  very  similar  to  the 
one  just  given.  It  consists  in  rolling  a  ball  of  mortar  and  then 
flattening  the  ball  to  the  thickness  of  half  an  inch.  The  consist- 
ency of  the  mortar  should  be  such  that  it  shall  neither  crack  in 
flattening  nor  run  at  the  edges.  These  pats  are  placed  in  a  vessel 
of  cold  water  immediately  after  gauging  and  heat  applied  and 
regulated  so  that  the  water  boils  in  about  an  hour.  The  boiling 
is  continued  for  three  hours,  when  the  pats  are  removed  and  ex- 
amined for  checking  and"  cracking.  Many  operators  after  steam- 
ing the  pats  for  five  hours  as  prescribed  by  the  standard  rules  and 
noting  the  results  place  the  pats  down  in  the  water  and  boil  for 
from  three,  to  five  hours. 

Calcium  Chloride  Test. 

Candlot  discovered  by  a  series  of  experiments  upon  cement 
that  if  the  cement  is  either  gauged  with  or  kept  in  water  contain- 
ing calcium  chloride  the  free  lime  in  it  is  slaked  much  more 
quickly.  The  more  concentrated  the  solution  the  more  marked  the 
effect.  The  action  of  the  salt  is,  therefore,  similar  to  that  of  heat, 
to  increase  the  chemical  action  causing  expansion.  If  the  cement 
is  guaged  with  a  concentrated  solution  of  calcium  chloride,  the 
lime  will  probably  all  be  slaked  before  the  cement  sets,  so  that 
no  cracking  will  occur  on  hardening,  even  if  much  free  lime  is 
present.  If,  however,  the  calcium  chloride  solution  is  more  dilute 
(40  grams  to  the  liter)  it  will  only  cause  slaking  of  a  very  small 
percentage  of  the  free  lime,  such  a  small  percentage  as  is  unobjec- 
tionable in  cements.  If  a  pat  made  of  this  mortar  is  then  kept  in  a 
calcium  chloride  solution  of  the  same  strength,  the  slaking  of  the 
rest  of  the  lime  will  be  greatly  hastened  and  crackling  will  soon 


356 


PORTLAND  CEMEXT 


appear  if  a  harmful  quantity  of  free  lime  is  present.  To  carry  out 
the  test,  gauge  the  cement  with  a  4  per  cent,  solution  (40  grams 
to  the  liter)  of  calcium  chloride,  make  into  pats  upon  glass  plates 
and  allow  to  set,  after  which  immerse  the  pats  in  the  cold  4  per 
cent,  solution  of  calcium  chloride  for  twenty-four  hours  and  then 
remove  and  examine  for  cracks,  softening,  etc. 

Banschinger's  Calipers. 

The  expansion  or  contraction  of  cement  during  hardening 
may  be  measured  directly  and  very  accurately  by  means  of  Bau- 
shinger's  caliper  apparatus  (Fig.  96).  By  means  of  this  instrument 


Fig.  96,  Bauschinger's  Caliper  Apparatus. 

changes  in  the  length  of  small  parallelopipedons,  100  mm.  long 
and  5  sq.  cm.  cross-section,  may  be  actually  measured  to  with- 
in 1/200  mm.  The  apparatus  consists  of  a  stirrup-shaped  caliper, 
having  a  fine  micrometer  screw  on  its  right  arm,  the  left  being  the 
support  of  a  sensitive  lever.  The  shorter  arm  of  this  lever  termi- 
nates in  a  blunt  caliper  point  and  is  pressed  against  the  measuring 
screw  by  a  spring  attached  to  the  long  arm.  The  calipers  are 
readily  moved  in  any  direction  and  the  micrometer  is  read  in  the 
usual  manner.  One  revolution  of  the  screw  equals  0.5  mm.  and 
the  readings  on  the  head  are  made  at  1/20o  mm.  The  specimen  is 
molded  with  square  cavities  in  the  end,  and  in  these  are  set  plates 


SOUNDNESS  357 

of  glass  containing  centers  for  the  caliper  points.  The  molding 
is  done  similar  to  that  for  tension  specimens  except  that  both  sides 
should  be  repeatedly  struck  off  smooth.  It  requires  but  a  few 
minutes  to  measure  a  specimen  by  this  apparatus. 

Lc  Chatelier's  Calipers. 

Le  Chatelier's  calipers  are  shown  in  Fig.  97.  This  apparatus 
consists  of  a  small  split  cylinder  of  spring  brass  or  other  suitable 
metal  of  0.5  mm.  (.oi97-in.)  in  thickness,  30  mm.  (i.i875-ins.) 
internal  diameter,  and  30  mm.  high,  forming  the  mold,  to  which 
on  either  side  of  the  split  are  attached  two  indicators  165  mm. 
(6.5-ins.)  long  from  the  centre  of  the  cylinder,  with  pointed  ends 
A  A,  as  shown  upon  the  sketch. 

Cylinder  of  Spring  Brass 


.-•\  or  other  Suitable  Metal 
\about  immin  thickness 


Plan. 


Eleva-Hon. 
Fig.  97,  ^e  Chatelier's  Calipers. 

This  apparatus  is  used  in  determinating  the  soundness  of  ce- 
ment in  Great  Britain,  where  the  standard  specifications1  demand 
that  the  cement  shall  not  show  a  greater  expansion  than  12  mm. 
after  having  been  spread  out  for  a  depth  of  3  inches  and  exposed 
to  the  air  for  24  hours  at  a  temperature  of  58°  to  64°  F.  The 
test  is  to  be  conducted  as  follows : 

The  mold  is  to  be  placed  upon  a  small  piece  of  glass  and  filled 
with  cement  gauged  in  the  usual  way,  care  being  taken  to  keep  the 
edges  of  the  molds  gently  together  while  this  operation  is  being 
performed.  The  mold  is  then  covered  with  another  glass  plate,  a 
small  weight  is  placed  on  this  and  the  mold  is  immediately  placed 
in  water  at  58°  to  64°  F.  and  left  there  for  24  hours. 

The  distance  separating  the  indicator  points  is  then  measured, 
and  the  mold  placed  in  cold  water,  which  is  brought  to  a  boiling 
point  in  15  to  30  minutes,  and  kept  boiling  for  six  hours.  After 
cooling,  the  distance  between  the  points  is  again  measured,  the 

i  Report — Committee  on  Cement,  Engineering  Standards  Committee. 


358  PORTLAND  CEMENT 

difference  between  the  two  measurements  represents  the  expan- 
sion of  the  cement,  which  must  not  exceed  the  limits  laid  down 
in  the  specification. 

OBSER  VA  TIONS. 
Importance  of  the  Test. 

The  most  important  quality  of  cement  is  soundness,  for  no 
matter  how  high  a  degree  of  tensile  strength  a  cement  may  devel- 
op at  comparatively  short  periods,  if  it  fails  to  resist  the  disinte- 
grating influences  of  the  atmosphere  or  the  water  in  which  it 
may  be  placed,  it  is  useless  as  a  material  of  construction.  This 
tendency  to  disintegrate,  fall  to  a  powder,  crack  or  expand  on 
mixing  the  cement  with  water  is  termed  ''blowing."  This  fault 
is  usually  due  to  improper  proportioning  of  the  raw  materials,  al- 
lowing an  excess  of  lime  over  what  will  combine  with  the  silica 
and  alumina  of  the  cement  mixture ;  or  an  improper  burning,  fail- 
ing to  raise  the  temperature  to  the  point  where  all  the  lime  may 
combine  with  the  silica  and  alumina,  thus  leaving  some  in  the  tin- 
combined  state;  or  from  insufficient  grinding  of  the  raw  mate- 
rials making  it  impossible  for  all  the  lime  to  come  in  contact  with 
and  unite  with  the  silica  and  alumina.  This  free  or  loosely  com- 
bined lime  on  coming  in  contact  with  water  is  slaked  and  ex- 
pands, causing  the  cement  to  crack  and  fall  to  pieces. 

Causes  of  Unsoundness. 

Some  discussion  has  been  aroused  of  late  as  to  what  causes  the 
failure  of  cement  to  stand  the  various  tests  for  soundness.  Some 
of  the  various  compounds  which  may  be  present  in  cement,  cal- 
cium di-silicate,  alkalies,  etc.,  are  said  to  promote  checking  in  the 
boiling  test.  All  authorities  seem  to  agree,  however,  that  the 
chief  cause  is  the  presence  of  free  or  unstable  lime  over  and  above 
a  certain  limit.  This  free  lime  slacks  after  the  cement  has  itself 
hardened  or  set,  causing  the  test-piece  to  warp  and  check  from 
the  expansion  set  up  by  the  change.  The  object  of  all  tests  for 
soundness  is,  therefore,  to  ascertain  if  the  maximum  of  free  lime 
that  may  safely  be  present  has  been  exceeded. 

A  certain  small  percentage  of  free  lime  is  present  in  all  cement. 
I  have  frequently  added  as  much  as  5  per  cent,  of  unslaked  lime 


SOUNDNESS 


359 


(prepared  from  precipitated  calcium  oxalate,  and  hence  very  fine- 
ly pulverized)  to  cement,  and  yet  pats  made  from  the  mixture 
passed  both  boiling  and  28-day  cold  tests.  If  the  lime  is  coarser, 
the  quantity  which  can  be  added  is  much  smaller.  Slaked  lime 
may  be  ad4ed  in  large  quantities  without  affecting  either  boiling 
or  cold  water  pats ;  so  may  also  carbonate  of  lime.  Pats  with  any 
proportion  of  either  are  perfectly  sound. 

Effect  of  Seasoning  on  Soundness. 

Anything  which  promotes  the  changing  over  of  the  free  lime 
into  slaked  lime  or  carbonate  of  lime  will,  therefore,  cause  cement 
at  first  unsound  to  become  sound.  The  air  always  contains  the 
elements,  moisture  and  carbon  dioxide,  to  bring  about  such  a 
change,  so  that  if  cement  that  is  unsound  is  stored  for  any  length 
of  time  it  will  gradually  become  sound,  from  the  slaking  and  car- 
bonating  of  the%  free  lime.  This  is  illustrated  by  the  following 
table : 
TABLE  XU.—  SHOWING  EFFECT  OF  SEASONING  ON  SOUNDNESS. 


Age  in  days 
after  being 
ground,  i 

Cement 
No.  i. 

Cement 
No.  2. 

Cement 
No.  3. 

Cement 

No.  4. 

Cement 
No.  5. 

Results  of  5  hour  steam  test  (A.  S.  C.  E.) 

Partly 

Entirely 

O 

Checked 

disinte- 

Checked 

Checked 

disinte- 

grated 

grated 

I 

Checked 

Badly 
Checked 

Checked 

0.  K. 

Entirely 
disinte- 
grated 

3 

Slightly 
Checked 

Badly 
Checked 

Slightly 
Checked 

Partly 
dislnte- 
§  rated 

7 

O.  K. 

Checked 

Slightly 
Checked 

adly 
Checked 

H 

Checked 

O.  K. 

Badly 
Checked 

21 

Slightly 
Checked 

Checked 

9  8 

O    K" 

PViprtrpH 

90 

O.  K. 

Cement  which  has  seasoned  sound  is  just  as  good  as  one  which 
was  sound  when  freshly  made,  and  the  writer  does  not  think  the 

1  Samples  were  seasoned  in  a  small  paper  bag  on  a  shelf  in  the  laboratory. 


360 


PORTLAND  CEMENT 


engineer  need  concern  himself  whether  the  manufacturer  prefers 
to  make  cement  which  is  sound  when  fresh,  or  whether  he  pre- 
fers to  age  it  sound  in  his  stock-house.  So  long  as  it  is  sound 
he  is  secure,  and  possibly  the  softer  burned  clinker,  usually  un- 
sound when  freshly  ground,  will  grind  with  a  greatep  percentage 
of  flour,  increasing  the  sand-carrying  capacity  of  the  cement. 

Effect  of  Fine  Grinding  of  the  Raw  Materials  on  Soundness. 

In  order  for  cement  to  stand  the  boiling  test  when  fresh  from 
the  grinding  mills,  the  raw  materials  must  be  finely  ground.  The 
unsoundness  due  to  coarse  grinding  of  the  raw  materials  is  prob- 

TABLE  XLII.—  SHOWING  EFFECT  OF  FINENESS  OF  GRINDING  OF 
CLINKER  ON  SOUNDNESS. 


Condition  of  Cement  as  Tested. 

Fineness. 

Result  of 
5  hours  steam  test. 
(A.  S.  C.  E.) 

Residvie 
No.  100. 

Residue 
No.  200. 

As  received  from  the  mills,  tested 

8-5 
8.5 

8-5 
o.o 

0.0 

o.o 

27.0 
27.0 
27.0 
0.0 
O.O 

o.o 

Partially  disintegrated 
Partially  disintegrated 
Badly  checked 
Sound 
Slightly  checked 

Sound 

As  received  from  the  mills,  tested 
again  after  seasoning  one  week. 
As  received  from  the  mills,  tested 
again  after  seasoning  one  month 
Portion  of  sample  passing  No.  200 
sieve,  tested  one  day  old  
Sample  ground  to  all  pass  a  No. 
200  sieve,  tested  one  day  old  •  •  • 
Sample  ground  to  all  pass  a  No. 
200  sieve,  tested  one  week  after 

grinding  

ably  the  hardest  form  of  unsoundness  to  cure  by  aging.  This  is 
particularly  so  if  the  clinker  has  been  burned  very  hard,  as  the 
coarse  pieces  of  limestone,  calcined  to  free  lime,  are  locked  up  in 
a  case  of  clinker.  If  this  case  is  not  broken  in  grinding,  the  free 
lime  is  left  surrounded  by  a  wall  of  clinker  and  will  be  very  slowly 
acted  on  by  the  moisture  of  the  air.  The  experiment  in  Table 
XLII  seems  to  prove  this  very  thing.  Laboratory  records  show 
the  unsoundness  of  this  sample  to  have  been  due  to  coarse  grind- 
ing of  the  raw  mixture.  The  fine  particles  passed  to  boiling 
test  fresh,  the  coarse  ones  failed  even  on  grinding,  but  on  aging 


SOUNDNESS 


36i 


one  week,  the  ground  particles  stood  the  test.  Aging  the  cement, 
however,  for  two  weeks  failed  to  make  it  sound,  because  the  free 
lime  was  locked  up  in  the  coarse  particles,  where  hydration  could 
only  take  place  very  slowly,  but,  on  grinding  the  coarse  particles, 
the  air  had  a  chance  to  get  at  the  free  lime  and  convert  it  to  the 
innocuous  hydroxide.1 

Effect  of  Fine  Grinding  of  Cement  Itself  on  Soundness. 
Fine  grinding  of  the  cement  itself  will,  even  without  aging, 
often  make  it  pass  the  boiling  test.     The  reason  for  this  is  that 
the  water  used  to  gauge  the  pat  can  get  at  the  lime  to  slake  it  be- 
fore the  cement  sets.    Table  XLJII  is  given  to  illustrate  this : 

TABLE  XLIII.— SHOWING  EFFECT  OF  FINE  GRINDING  ON 
SOUNDNESS. 


Cement  No. 

Results  of  5  hour  steam  test  A.  S.  C.  E.) 

As  received. 

Ground  to  pass 
No.  200. 

Ground  to  an  im- 
palpable powder. 

I 
2 
3 

4 

Checked 
Checked 
Checked 
Checked 

Sound 
Sound 
Slightly  checked 
Slightly  checked 

Sound 
Sound 

Effect  of  Sulphates  on  Soundness. 

Pats  allowed  to  harden  in  steam  or  hot  water  will  often  pass 
the  boiling  test  where  pats  hardened  in  air  will  not.  It  must  be 
remembered  that  checking  is  caused  by  slaking  after  the  pats  are 
fully  hardened.  If  they  are  placed  in  steam  to  harden  the  moist 
air  merely  accelerates  the  slaking  of  the  lime,  doing  the  work  be- 
fore the  pat  hardens,  just  as  heat  hastens  any  chemical  action. 
The  addition  of  sulphates,  either  as  gypsum  or  plaster  of  Paris, 
aids  the  cement  in  standing  the  boiling  test,  probably  because  it 
delays  the  set  until  after  the  lime  has  slaked.  The  rendering  of 
the  free  lime  inert  by  the  formation  of  compounds  with  the  lime 
by  the  gypsum  seems  hardly  probable,  since  the  lime  and  gypsum 
could  not  react  unless  both  were  in  solution,  and  if  the  water 

I  See  also  Taylor,  Proceedings  Am.  Soc.  Test.  Mat.,  III.,  (1903),  377,  and  Butler,  Port- 
land Cement,  p.  174. 


362 


PORTLAND  CEMENT 


could  get  at  the  free  lime  to  dissolve  it,  slaking  would  take  place 
on  adding  water  only,  and  the  harmless  hydroxide  would  be 
formed.  The  early  hardness  due  to  gypsum  can  hardly  play  any 
part,  since  cements  breaking  as  high  as  600  pounds  in  24  hours 
may  fail  on  the  boiling  test,  while  briquettes  breaking  at  150 
pounds  may  be  sound.  My  own  experiments  go  to  show  that  any- 
thing which  will  delay  the  setting  of  cement  until  after  the  free 
lime  has  slaked,  or  that  will  hasten  the  slaking  of  the  free  lime 
before  the  pat  sets,  will  make  cement  sound.  The  table  given  be- 
low shows  the  effect  of  additions  of  plaster  on  the  boiling  test : 

TABLE  XLIV  SHOWING  EFFECT   OF  ADDITIONS  OF  GYPSUM  OR 
PLASTER  OF  PARIS  ON  SOUNDNESS. 


Sample. 

Percent. 
S03 

Result  of  5  hour  steam  test  (A.  S.  C.  E.)1 

0.5  Per  cent. 
Plaster  added. 

i.o  Per  cent. 
Plaster  added. 

2.0  Per  cent. 
Plaster  added. 

3.0  Per  cent. 
Plaster  added. 

1.  21 

1-43 
i.iS 

1-36 
0.31 

Sound 
Checked 
Checked 
Checked 
Checked 

Sound 
Checked 
Checked 
Checked 

Sound 
Checked 
Sound 

Sound 

Ground  clinker 

Value  of  Accelerated  Tests. 

At  the  1903  meeting  of  the  American  Society  for  Testing 
Materials  Mr.  W.  P.  Taylor,  of  the  Philadelphia  Testing  Labo- 
ratory, read  a  very  carefully  prepared  paper  upon  the  boiling  test? 
in  which  he  compared  the  results  of  neat  briquettes  and  neat  pats 
with  the  results  of  the  boiling  test.  As  is  usual,  he  considered  a 
falling  off  of  the  strength  of  neat  briquettes  on  long  time  tests 
and  a  cracking  and  warping  of  the  neat  cold  water  pat  as  being 
positive  evidence  of  the  presence  of  injurious  constituents  in  the 
cement.  He  gives  these  figures :  "Of  all  the  samples  failing  to 
pass  the  boiling  test  34  per  cent,  of  them  developed  checking  or 
curvature  in  the  normal  pats  or  a  loss  of  strength  in  less  than  28 
days.  Of  those  samples  that  failed  in  the  boiling  test  but  re- 

1  All  samples  were  unsound  without  addition  of  plaster  of  Paris. 

2  Proceedings  Amer.  Soc.  Test.  Mat  ,  III.,  (1903),  374. 


SOUNDNESS  363 

mained  sound  for  28  days,  3  per  cent,  of  the  normal  pats  showed 
checking  or  abnormal  curvature  in  2  months,  7  per  cent,  in  3 
months,  10  per  cent,  in  4  months,  26  per  cent,  in  6  months,  and 
48  per  cent,  in  one  year;  and  of  these  same  samples  37  per  cent, 
showed  a  falling  off  in  tensile  strength  in  2  months,  39  per  cent, 
in  3  months,  52  per  cent,  in  4  months,  63  per  cent,  in  6  months, 
and  71  per  cent,  in  one  year.  Or  taking  all  these  together,  of  all 
the  samples  that  failed  in  the  boiling  test  86  per  cent,  of  them 
gave  evidence  in  less  than  a  year's  time  of  possessing  some  injur- 
ious quality. 

"On  the  other  hand,  of  those  cements  passing  the  boiling  test 
but  one-half  of  I  per  cent,  gave  signs  of  failure  in  the  normal  pat 
tests  and  but  13  per  cent,  showed  a  falling  off  in  strength  in  a 
year's  time." 

It  is  unfortunate  that  the  test  which  seems  to  be  accepted  by 
the  majority  as  a  standard  is  the  long-time  cold-water  pat,  a  test 
requiring  such  length  of  time  for  its  completion  as  to  practically 
forbid  its  use.  The  conditions  of  the  case  demand  a  rapid  test  in 
order  that  the  consumer  may  not  be  required  to  store  the  cement 
for  a  long  period  of  time  while  he  awaits  the  results  of  his  cold- 
water  pats. 

To  the  manufacturer  the  steam  and  boiling  tests  are  exceeding- 
ly useful,  for  if  a  cement  wrill  pass  these  tests  it  will  pass  any  test 
to  which  it  may  be  subjected.  He  can  »ot  hold  his  cement  in  his 
stock-house  for  months  while  he  ascertains  if  it  will  pass  the  cold- 
water  pat  test  and  so  he  applies  an  accelerated  test  to  tell  him  if 
this  cement  will  pass  the  tests  to  which  it  is  likely  to  be  put.  To 
my  mind  there  is  a  strong  comparison  between  the  steam  test  and 
the  color  test  for  carbon,  so  much  used  in  the  steel  works  labora- 
tories. While  this  latter  test  is  very  useful  to  the  manufacturer 
still  no  engineer  would  condemn  steel  on  the  result  .of  such  a  test, 
for  though  it  may  give  correct  results  in  nine  out  of  ten  cases  he 
does  not  care  to  take  the  risk  of  this  being  the  tenth  case  and  of 
throwing  out  a  good  steel,  and  so  working  great  hardship  to  the 
manufacturer. 

Unquestionably  much  good  concrete  has  been  made  from  so- 
called  unsound  cement,  and  this  is  the  key  to  the  whole  objection 


364  PORTLAND  CEMENT 

to  the  hot  test.  It  is  probable  that  much  of  the  first  American 
Portland  cement  would  not  have  passed  the  steam  test,  yet  it  is 
upon  the  merits  of  the  work  done  with  this  cement  that  engineers 
are  now  using  American  instead  of  imported  cement.  Butler 
gives  a  strong  plea  for  the  Faija  test  and  states  that  in  the  twenty 
years  this  test  has  been  in  use,  no  cases  of  failure  in  work  by  ce- 
ment passing  this  test  have  come  under  his  observation.  If  the 
Faija  test  is  severe  enough  to  exclude  all  bad  cements,  then  the 
boiling  test  is  needlessly  severe  as  it  rejects  many  cements  which 
pass  Faija's  test. 

All  cement  probably  contains  some  free  lime.  From  the  nature 
of  the  case  this  must  be  so,  since  cement  raw  materials  are  not 
ground  to  a  degree  of  fineness  nor  carried  to  a  state  of  fusion 
which  would  permit  of  every  molecule  of  lime  coming  in  contact 
with  a  molecule  of  silica  or  of  alumina.  Now  there  are  limits  be- 
yond which  if  the  uncombined  or  free  lime  goes,  certain  results 
will  take  place.  Let  us  suppose  that  with  a  very  small  percentage 
present  the  cement  will  fail  on  the  boiling  test  but  pass  satisfac- 
torily five  hours  in  steam,  and  if  a  still  larger  percentage  is  pres- 
ent it  will  fail  in  the  steam  but  pass  the  Faija  test.  Now,  again, 
let  us  suppose  that  a  neat  mixture  with  a  certain  small  percentage 
of  free  lime  is  sound,  with  a  larger  percentage  a  3  :i  sand  mixture 
is  sound,  with  a  still  larger  percentage  a  i  13  :8  concrete  is  sound. 
(It  is  well  understood  that  the  tendency  of  cement  to  disintegrate 
is  greater  in  a  neat  paste  than  in  a  sand  mixture,  and  anyone  with 
experience  in  cement  testing  knows  of  cases  where  neat  bri- 
quettes were  disintegrated  in  time  and  yet  the  sand  ones  were 
sound  and  strong).  Now  how  do  we  know  that  the  limit  of  lime 
which  may  be  present  in  good  cement  (that  is  cement  which  will 
make  "enduring  concrete)  is  coincident  with  that  maximum  which 
may.  be  present  for  a  sound  boiling  test  ? 

Nearly  all  advocates  of  the  steam  test  have  tried  to  prove  these 
two  limits  coincident  by  comparing  the  steam  test  with  the  results 
of  neat  pats  and  neat  briquettes.  Usually  the  coincidence  of  a 
failure  on  the  boiling  test  with  either  a  warping  or  cracking  of 
the  neat  pats  or  a  loss  of  strength  in  the  neat  briquettes  on  long 
time  tests  is  considered  competent  evidence  in  favor  of  the  boil- 


SOUNDNESS  365 

ing  test.  In  reality  cement  is  seldom  used  neat.  A  cement  which 
fails  on  the  boiling  test,  whose  neat  briquettes  fall  off  in  strength 
after  7  or  28  days,  yet  whose  sand  briquettes  increase  in  strength 
as  they  grow  older,  has  certainly  given  evidence  that  it  will  make 
good  concrete.  In  weighing  evidence  for  any  test  it  must  be  re- 
membered that  we  do  not  make  the  soundness  test  to  see  if  neat 
briquettes  will  fail  in  strength  as  they  age  or  if  neat  pats  will 
warp  and  decay,  but  whether  sidewalks,  piers,  abutments,  founda- 
tions, walls,  floors  and  buildings  of  concrete,  not  neat  cement,  will 
be  permanent,  and  the  thing  therefore  to  compare  the  boiling  test 
with,  is  concrete.  Not  until  we  can  compare  our  laboratory 
records  with  many  examples  of  both  failures  and  successes  in 
actual  work  will  we  have  reliable  data  for  forming  our  conclu- 
sions as  to  the  reliability  of  the  various  tests  for  soundness. 

Experiments  made  by  a  committee  of  the  Society  of  German 
Portland  Cement  Manufacturers  in  connection  with  the  Royal 
Testing  Laboratory  at  Charlottenburg  forced  them  to  report  in 
1900  and  again  in  1903  that  none  of  the  so-called  accelerated 
tests  for  consistency  of  volume  was  adapted  to  furnish  a  reliable 
and  quick  judgment  in  all  cases  concerning  the  applicability  of  a 
cement.  The  experiments  which  they  made  consisted  in  putting 
the  cement  into  actual  work  and  observing  it  during  a  period  of 
four  years.  The  committee  recommended  the  28-day  cold  water 
pat  as  a  standard  test.  If  this  test  is  taken  as  a  standard  the  hot 
test  will  reject  two  good  cements  for  every  bad  one. 


MISCELLANEOUS. 


CHAPTER  XVIIL 


THE  DETECTION  OF  ADULTERATION  IN 
PORTLAND  CEMENT. 


Cements  are  adulterated  with  natural  cement,  blast-furnace  slag, 
ground  limestone,  shale,  ashes,  etc.  Some  of  these  substances  are 
so  similar  to  Portland  cement  that  chemical  analysis  fails  to  show 
their  presence.  It  is,  therefore,  necessary  to  direct  special  tests 
to  their  detection.  When  present  in  small  quantities,  it  is  probable 
that  even  such  tests  will  fail  to  show  positively  an  adulterated 
cement. 

Tests  of  Drs.  R.  and  W.  Fresenins. 

Drs.  R.  and  W.  Fresenius,1  at  the  request  of  the  Association  of 
German  Cement  Manufacturers,  made  investigations  into  the  sub- 
ject of  cement  adulteration  looking  to  a  method  of  detecting  the 
same.  They  experimented  upon  twelve  samples  of  pure  Portland 
cement  from  Germany,  England  and  France,  and  compared  the 
results  of  tests  upon  these  with  the  results  obtained  by  similar 
tests  upon  three  kinds  of  hydraulic  lime,  three  kinds  of  weathered 
slag,  and  two  of  ground  slag.  The  cements  were  of  various  ages 
and  had  been  exposed  to  the  air  for  various  lengths  of  time.  On 
the  next  page  are  tabulated  their  experiments  for  comparison. 

Proposed  Tests. 

As  the  result  of  these  experiments  they  proposed  the  following 
tests  for  the  detection  of  adulteration : 

1.  The  specific  gravity. 

This  must  not  be  lower  than  3.10. 

2.  The  loss  on  ignition. 

This  should  be  between  0.3  and  2.59  per  cent. ;  certainly  not 
much  more. 

3.  The   alkalinity   imparted   to   water.      0.5   gram   of   cement 

1  Ztschr.  anal.  Chem.,  23,  175,  and  24,  66. 


ADULTERATION    IN    PORTLAND    CEMENT 


367 


should  not  render  50  cc.  of  water  so  alkaline  as  to  require  more 
than  6.25  cc.  nor  less  than  4  cc.  of  decinormal  acid  to  neutralize. 

4.  The  volume  of  normal  acid  neutralized. 

One  gram  of  cement  should  neutralize  from  18.8  to  21.7  cc.  of 
normal  acid. 

5.  The  volume  of  potassium  permanganate  reduced. 

One  gram  of  cement  should  reduce  not  much  more  than  0.0028 
gram  of  potassium  permanganate. 

TABLE  XLV.— ADULTERATION  IN  PORTLAND  CEMENT. 


i 

2 

3 

4 

5 

,. 

O 

HI 

If 

OS 

G  cs 

•il 
xS 

•? 

SD 

•St'o'd 

cj 

35 

gfc 

Description. 

CC 

bJD 

£   .'0 

la 

O  cO 

rj 

o 

^'  '  fe  ^    i 

3    . 

o  ^ 

O  ^ 

I 

I 

I5if 

5*0  & 

u 

•*->  o 

•S  3 
.OfO 

til 

O  rt  « 

Per  cent. 

5 

^ 

* 

• 

CC. 

mg. 

mg. 

Portland  cement,  A  .  .  . 

3.155 

1-58 

6.25 

20.71 

0.79 

•4 

B... 

3-125 

2-59 

4.62 

21.50 

2.38 

.6 

c... 

3-155 

2.  II 

4-50 

20.28 

°-93 

.8 

D... 

3-144 

I.98 

5-10 

21.67 

1.  12 

.0 

'             '          E--  • 

3-144 

1.25 

6.12 

19.60 

0.98 

.6 

F... 

3-134 

2.O4 

4.95 

20.72 

1.  21 

.1 

'              '           O 

3-J44 

0.71 

4-3° 

22.20 

0.89 

0.0 

H... 

3-125 

1.1  1 

4.29 

20.30 

1.07 

0.7 

J... 

3.134 

I.OO 

4.00 

19.40 

2.01 

0.0 

K... 

3-144 

0.34 

4.21 

20.70 

0.98 

0.0 

'               '            T 

3.154 

1.49 

4.60 

1  8.  80 

2.80 

0.3 

M  •  •  • 

3.125 

5.50 

20.70 

2-33 

0.0 

Hydraulic  lime      A... 
B... 

2.441 
2-551 

18.26 

17.82 

20.23 
22.73 

21-35 
26.80 

1.40 
0-93 

27.8 
31.3 

c... 

2.520 

19.60 

19.72 

19.96 

0.98 

47-7 

Weathered  slag     A  ... 

3.012 

0.76 

0.91 

14.19 

74.60 

3-6 

B... 

3-003 

1.92 

0.70 

13.67 

60.67 

3-5 

c... 

2.967 

I.  II 

I.OO 

9.70 

44-34 

2.9 

Ground  slag            I  ... 

3-003 

0.32 

0.31 

3-6o 

64.40 

2.4 

II... 

2-873 

0.43 

0.1  1 

8.20 

73-27 

2.2 

6.  The  weight  of  carbon  dioxide  absorbed. 

Three  grams  of  cement  should  not  absorb  more  than  0.0018 
gram  of  carbon  dioxide. 

The  tests  i,  3,  4,  and  5  are  for  the  detection  of  slag  and  i,  2, 
3  and  6  for  the  detection  of  hydraulic  lime. 


PORTLAND  CEMENT 

Drs.  R.  and  W.  Fresenius  also  tried  these  tests  upon  experimen- 
tal mixtures  containing  10  per  cent,  of  slag  or  hydraulic  lime, 
and  in  each  case  were  able  to  detect  the  impurity. 
Carrying  Out  the  Tests. 

The  methods  employed  for  carrying  out  the  tests  were  as  fol- 
lows : 

1.  They  used   for  taking  the   specific  gravity   the   method   of 
Schumann  (see  page  280),  with  turpentine  as  the  liquid.   The  end 
of  the  tube  was  corked  to  prevent  evaporation,  the  temperature 
•kept  constant,  and  the   vessel   carefully   shaken   to  displace   air 
bubbles. 

2.  For  loss  on  ignition  2  grams  of  cement  were  weighed  into  a 
tared  crucible,  and  then  heated  over  a  Bunsen  burner  for  twenty 
minutes.     The  loss  shown  on  again  weighing  was  the  loss   on 
ignition. 

3.  For   the    "alkalinity    to    water   test."      The    substance    was 
finely  powdered  and  passed  through  a  sieve  of  5,000  meshes  to  the 
square  centimeter.1    Of  the  resulting  powder,  i  gram  was  shaken 
up  with  100  cc.  of  distilled  water  without  warming  for  ten  min- 
utes.    The  solution  was  then  passed  through  a  dry  filter  paper 
into  a  dry  vessel  and  50  cc.  of  the  filtrate  titrated  with  decinormal 
hydrochloric  acid.2 

4.  For  "standard  acid  necessary  to  decompose/'     One  gram 
of  the  fine  powder  obtained  in  3  was  shaken  with  30  cc.  of  normal 
hydrochloric  acid3  and  70  cc.  of  water  for  ten  minutes,  without 
warming,  and  filtered  through  a  dry  filter  paper  50  cc.  of  the 
filtrate  were  then  titrated  with  normal  caustic  soda.4 

5.  For  the  volume  of  permanganate  reduced.     One  gram  of 
the  fine  powder,  obtained  in  3,  was  treated  with  a  mixture  of  50 
cc.  of  dilute  sulphuric  acid  (sp.  gr.  1.12)   and  100  cc.  of  water. 

1  32,260  meshes  to  the  square  inch. 

2  To  make  decinormal  hydrochloric  acid,  refer  to  page  233,  with  the  notes  under  this 
section,  and  taking  such  a  quantity  of  dilute  hydrochloric  acid  as  contains  3.65  grams  of 
HC1,  dilute  this  volume  to  i  liter.     Check  its  value  by  one  of  the  methods  given  in  the  sec- 
tion referred  to.     The  '2I^  N  nitric  acid  may  be  diluted  to  Vio  N  strength  and  used  in  place 
of  the  1/10  N  hydrochloric  acid. 

a  Normal  acid  should  contain  36.5  grams  HCI,  per  liter. 

4  To  prepare  normal  caustic  sola,  refer  to  pige  232,  and  using  the  above  normal  acid  as 
a  standard  proceed  as  directed  there.  The  2;,-  x  solutions  used  in  checking  the  per  cent, 
of  lime  in  cement  mixture  (see  page  232)  may  be  used  for  this  test.  In  this  case  shake  up 
the  cement  with  a  mixture  of  75  cc.  of  2/5  normal  acid  and  25  cc.  of  water,  and  titrate  back 
with  the  2/5  normal  alkali. 


ADULTERATION    IN    PORTLAND    CEMENT  369 

The  resulting  solution  was  then  titrated  with  potassium  perman- 
ganate solution.1 

6.  For  carbon  dioxide  absorbed,  about  3  grams  of  the  fine  pow- 
der obtained  as  in  3,  were  placed  in  a  weighed  tube  and  a  stream 
of  carbon  dioxide  allowed  to  pass  over  it.  The  sample  was  then 
dried  in  a  desiccator  over  sulphuric  acid  (sp.  gr.  1.184)  and 
weighed.  The  increase  in  weight  gave  the  amount  of  carbon 
dioxide  absorbed,  a  small  calcium  chloride  drying  tube  was  placed 
after  the  tube  containing  the  cement  to  absorb  any  water  evolved. 
Le  Chatelier' s  Test. 

Le  Chatelier  has  devised  a  very  neat  test  for  the  adulteration 
in  cement,  depending  upon  the  lower  density  of  the  adulterant 
than  of  the  cement.  His  method  consists  in  separating  these 
lighter  impurities  from  the  cement  by  means  of  a  heavy  liquid, 
a  mixture  of  methyl  iodide  and  benzene,  prepared  of  such 
strength  that  they  float  upon  its  surface  while  the  pure  Portland 
sinks  to  the  bottom. 

This  method  is  in  use  in  the  Philadelphia  City  Testing  Labora- 
tory and  gives  good  satisfaction  there,  where  it  is  used  to  detect 
additions  of  Rosendale  to  Portland  cement.2 

Preparation  of  the  Heavy  Liquid. 

As  the  first  step  the  methyl  iodide  solution  must  be  prepared. 
This  should  be  of  density  2.95  according  to  Le  Chatelier.  As  the 
density  of  the  methyl  iodide  itself  is  3.1,  benzene  must  be  added 
in  small  quantities  until  a  crystal  of  aragonite  (serving  as  a 
guide)  whose  density  is  2.94  just  remains  at  the  surface.  Since 
very  small  quantities  of  benzene  change  the  density  of  the  methyl 
iodide  considerably  it  is  well  to  make  two  solutions,  one  a  little 
above  and  one  a  little  below  the  density  sought,  and  then  to  add 
the  one  to  the  other  until  the  required  density  is  obtained.  By 
this  means  a  more  gradual  change  is  affected  and  the  danger  of 
over-running  the  mark  is  lessened. 

Apparatus. 

Le  Chatelier  used  in  his  experiments  a  little  glass  tube  10  mm. 

1  Dissolve  0.28  gram  of  KMnO4  in  100  cc.  of  water.     Not  much  more  than  i  cc.  of  this 
solution,  or  2  cc.  of  the  solution  used  to  determine  ferric  oxide  in   cement   should  be  re- 
quired if  the  cem?nt  is  unadulterated. 

2  Taylor,  Chem.  Eng.,l.,  258. 


37°  PORTLAND  CEMENT 

in  diameter  and  70  mm.  long.  The  tube  (Fig.  98)  is  widened  at 
the  top  to  a  funnel  and  drawn  at  the  bottom  with  a  regular  slope 
to  an  opening  of  I  mm.  diameter.  This  opening  is  closed  on  the 
interior  a  little  above  the  bottom  by  a  plunger  consisting  of  a 

o 


Fig  98.     Separatory  Funnel  for  Methyl  Iodide  Solutions. 

small   emery  ground-glass   stopper  on  the  end   of  a   glass   rod 
which  projects  above  the  funnel  top. 

Test. 

To  make  a  test  the  stopper  is  wet  with  water  to  make  a  tight 
joint  and  inserted  into  the  opening  of  the  tube.  Grease  cannot  be 
used  as  it  is  dissolved  by  the  methyl  iodide  solution.  Ten  grams  of 
the  suspected  cement  are  weighed  into  the  tube  and  5  cc.  of 
methyl  iodide  solution  (sp.  gr.  2.95),  prepared  as  above,  poured 
upon  it.  A  thin  platinum  wire  bent  into  a  loop  around  the  plun- 
ger is  then  moved  around  and  up  and  down  in  the  liquid  in  a 
lively  manner  in  order  to  drive  out  all  air  bubbles  and  mix  the 
cement  and  liquid  thoroughly.  The  apparatus  is  now  set  aside 
for  an  hour,  when  it  will  be  found  that  the  slag  is  on  top  and  the 
cement  below.  The  apparatus  is  now  placed  over  a  dry  filter,  the 
stopper  raised  and  the  cement  and  part  of  the  liquid  allowed  to 
run  out.  The  cement  is  retained  upon  the  filter  while  the  liquid 
is  caught  in  a  vessel  below  and  may  be  used  again.  The  slag  and 
the  rest  of  the  liquid  are  then  run  out  upon  another  filter,  and  the 
excess  of  liquid  caught  in  a  vessel  for  use  again.  The  filters  con- 
taining the  slag  and  cement  are  washed  with  benzene,  dried  and 
weighed  separately.  From  the  weights  the  percentage  of  adultera- 


ADULTERATION    IN    PORTLAND    CEMENT  3/1 

tion  can  be  calculated.    The  slag  and  cement  can  then  be  analyzed 
chemically,  if  thought  necessary,  as  a  further  guide. 

Microscopic  Test. 

The  microscope  furnishes  us  with  a  very  good  means  of  detect- 
ing added  material  in  cement.  Butler1  recommends  that  those 
particles  which  pass  a  76  sieve  and  are  retained  upon  a  120  sieve 
be  examined  with  a  low  power  (say  one-inch)  objective.  The 
particles  of  pure,  well-burned  cement  clinker  of  this  size  will  then 
appear  dark,  almost  black  in  color,  resembling  coke  somewhat, 
and  will  possess  the  characteristic  spongy  honey-combed  appear- 
ance of  cement  clinker.  The  particles  of  less  well-burned  clinker, 
always  present  in  cement,  will,  when  examined  in  the  same  way, 
present  the  same  shape  and  structure,  but  will  differ  in  color, 
being  light  brown  and  semi-transparent,  resembling  gum  arabic. 
Intermediate  products  range  from  black  to  light  brown.  These 
particles  are  always  of  a  more  or  less  rounded  nature.  Particles 
of  slag  of  the  same  size  viewed  under  the  same  conditions  differ 
somewhat  in  color,  according  to  the  nature  of  the  slag.  Usually 
the  particles  are  light  colored,  of  angular  fracture,  and  instead  of 
the  particles  presenting  a  rounded  appearance  the  edges  are 
sharp  like  flint.  Not  to  be  mistaken  for  the  slag,  however,  are  the 
particles  of  pebbles  from  the  tube-mills  used  to  grind  the  clinker. 
These  latter  may  be  distinguished  from  the  slag  by  picking  out 
the  particles  in  question  with  a  pair  of  pincers,  crushing  them  in 
a  small  agate  mortar  and  treating  them  with  hydrochloric  acid. 
The  slag  is  readily  attacked  while  the  debris  from  the  pebbles  is 
not  attacked.  Particles  of  iron  from  the  crushers  are  also  pres- 
ent in  the  residue  caught  upon  the  120  sieve.  These  may  be 
identified  by  their  black  metallic  appearance  and  their  behavior 
with  the  magnet.  Neither  of  these  can,  of  course,  be  considered 
as  adulterants.  Limestone  and  cement  rock  if  present  are  in  more 
or  less  flattened  particles,  and  the  latter  is  always  dark  gray  in 
color.  Both  of  these  may  be  readily  detected  by  effervescence 
with  dilute  acids.  The  foreign  particles  may  also  be  picked  out 
of  the  residue  with  a  pair  of  tweezers,  ground  finely  and  identified 
by  chemical  analysis. 

1  '•'•Portland  Cement,'1''  p.  273. 


CHAPTER  XIX. 


TRIAL  BURNINGS. 


In  prospecting  new  deposits  of  raw  materials,  it  is  often 
thought,  advisable  to  make  up  small  trial  lots  of  cement  in  the 
laboratory  and  examine  into  the  physical  properties  of  these.  For 
such  trials,  it  is  necessary  to  crush  the  raw  materials,  if  they  are 
not  already  in  small  pieces,  and  correctly  proportion  them.  The 
mixture  is  then  finely  ground,  the  powder  moistened  with  water 
and  moulded  into  little  cubes  or  balls  and  these  latter  are  burned 
in  some  form  of  laboratory  kiln.  The  resulting  clinker  is  then 
sorted  to  separate  out  the  under-burned  and  the  hard-burned  por- 
tions are  ground  to  the  same  degree  of  fineness  as  commercial 
cement.  It  is  also  often  desirable  to  make  experimental  burnings 
in  the  investigation  of  the  various  problems  which  arise  in  con- 
nection with  the  manufacture  and  properties  of  cement.  The 
apparatus  described  below  is  suitable  for  such  purposes  and  has 
been  used  in  similar  work  by  various  investigators. 

For  crushing  the  raw  rock  small  Blake  or  Bosworth  crushers 
such  as  are  used  in  almost  all  laboratories  for  crushing  ores  will 
be  found  convenient.  These  can  be  so  adjusted  as  to  crush  the 
rock  to  about  wheat  size  and  finer.  They  can  be  obtained  either 
hand  or  power  driven,  but  for  the  work  indicated  above  they 
should  be  power  driven  and  attached  to  a  shafting  somewhere 
about  the  mill  or  run  by  an  independent  motor.  After  crushing 
the  materials  to  the  size  indicated  above  they  should  be  carefully 
analyzed  and  mixed  in  the  proper  proportions  (see  Chapter  IV). 
The  mixture  should  then  be  finely  ground.  The  degree  of  fine- 
ness should  be  indicated  by  the  nature  of  the  investigation.  If  a 
test  is  being  made  of  the  suitability  of  certain  raw  materials  the 
mixture  should  be  ground  no  finer  than  it  would  be  in  actual  mill 
practice,  or  about  95  per  cent,  through  a  100  mesh  sieve. 

Samples  of  clay  and  marl  should  be  thoroughly  dried  before 


TRIAL  BURNINGS 


373 


analyzing  and  proportioning  them.    This  can  be  done  over  a  hot 
plate  or  steam  radiator,  etc. 

For  finely  grinding  the  mixture,  a  jar  mill  will  be  found  as 
convenient  as  anything  else.  Fig.  99  shows  the  form  (made  by 
the  Abbe  Engineering  Co.)  which  the  writer  has  used  in  his 
laboratory  and  found  very  satisfactary.  This  consists  of  a  porce- 
lain jar,  the  cover  of  which  is  fastened  tightly  on  by  means  of  a 
clamp,  as  shown.  The  jar  itself  is  held  in  a  revolving  frame  by 
brass  bands,  one  of  which  can  be  loosened  by  means  of  a  thumb 


COPYRIGHTL1904,   BY  ABBE  ENGINEERING  Co. 

Fig-  99,  Jar  Mill. 

screw,  allowing  the  jar  to  be  removed  from  the  frame.  The  jar 
is  filled  half  full  of  porcelain  balls  and  as  the  former  revolves  the 
material  is  ground  by  the  latter.  The  jar  is  intended  to  make 
from  40  to  50  revolutions  per  minute  and  will  grind  about  15 
pounds  of  material  at  a  charge. 

After  grinding  finely,  the  powder  is  mixed  with  water  until  it 
is  plastic  and  then  moulded  into  small  cubes  or  balls.  The  writer 
has  usually  found  it  an  excellent  plan  to  roll  the  mass  out  in  a 
thin  sheet  on  a  pane  of  glass  and  then  cut  this  into  thin  strips 
with  the  point  of  a  spatula  or  trowel.  These  strips  .on  drying 
usually  break  up  at  right  angles  into  small  cubes.  If  they  do  not, 
the  breaking  can  then  be  done  by  hand.  The  size  of  the  balls  or 


374 


PORTLAND  CEMENT 


cubes  will  depend  upon  the  size  of  the  furnace — a  small  furnace 
will  require  a  smaller  ball  than  a  larger  one.  They  should  not, 
however,  be  smaller  than  a  pea  for  even  a  small  furnace. 


£ 


Fig.  100,  Furnace  for  Experimental  Burnings. 

For  burning  small  quantities  of  cement  the  writer  has  found 
the  form  of  kiln  shown  in  Fig.  100  useful.  It  consists  of  a  large 
Battersea  crucible  (size  R)  13  inches  in  height  and  10  inches  in 
diameter,  resting  on  a  piece  of  fire-brick,  C,  and  fitting  snugly  into 
a  cylinder  of  concrete,  B.  The  crucible  is  punched  with  four 
holes  F,  F,  F,  F,  around  its  bottom  and  through  these  the  air 


TRIAL  BURNINGS  375 

for  cumbustion  enters  the  crucible.  A  tight  joint  between  the 
crucible  and  the  concrete  cylinder  is  made  by  means  of  fire-clay 
or  wet  asbestos  as  shown  at  E,  E.  Air  is  brought  into  the  con- 
crete cylinder  by  means  of  the  pipe  D.  F,  F,  is  a  sheet  iron 
jacket  surrounding  the  cylinder  of  concrete.  The  walls  of  the 
cylinder  are  about  6  inches  thick.  Air  for  burning  may  be 
obtained  from  a  compressor  or  a  small  Root  or  Crowell  blower. 
Larger  crucibles  than  the  size  indicated  can  be  obtained  when  a 
larger  furnace  is  needed.  The  one  given  above  will  burn  3  or 
4  pounds  of  cement.  Charcoal  or  oil  coke  is  used  as  a  fuel.  A 
small  piece  of  cotton  waste  saturated  with  oil  is  placed  in  the 
crucible  and  when  this  is  burning  a  few  handfulls  of  charcoal 
are  added  and  the  air  blast  turned  on.  As  soon  as  the  charcoal  is 
burned  and  the  crucible  is  heated  up,  it  "is  filled  half  full  of  char- 
coal and  the  little  balls  of  slurry  are  added  in  a  thin  layer.  More 
charcoal  is  placed  over  this  and  then  more  slurry,  etc.,  until  the 
crucible  is  full.  A  pair  of  fire  bricks  having  an  inch  channel  cut 
in  one  side  of  each  is  then  placed  over  the  crucible  to  form  a 
cover  and  the  heating  continued  until  all  the  charcoal  is  burned 
away.  The  air  is  left  turned  on  to  cool  the  clinker  after  which 
the  latter  is  sorted. 

For  research  work  when  contamination  with  the  fuel  ash  is 
objectionable,  a  small  Fletcher  furnace  lined  with  a  mixture  of  90 
parts  coarse,  burned  magnesite  and  10  parts  Portland  cement  will 
be  found  useful. 

Bleininger  describes1  a  kiln  used  in  the  Ohio  State  Univer- 
sity Ceramic  Department.  This  consists  of  a  straight  shaft 
of  fire-brick  with  walls  4  inches  thick,  divided  into  three 
distinct  divisions.  Air  is  forced  into  a  space  4  inches  high 
at  the  bottom  under  a  pressure  of  about  12  ounces  from  a 
blower  through  a  2-inch  pipe.  This  space  is  divided  from  the 
next  division  by  means  of  a  cast-iron  plate  provided  with  concen- 
tric rows  of  holes.  Above  this  plate  about  5  inches  away  from  it 
an  iron  pan  is  supported  by  two  bricks.  Petroleum  is  fed  into 
this  pan  by  means  of  a  ^J-inch  pipe,  running  in  by  gravity  from 
a  can  some  distance  away.  Several  inches  above  the  pan  the 

1  Ohio  Geol.  Survey,  Bui.  No.  3  [IV.]  Manufacture  of  Hydraulic  Cements. 


PORTLAND  CEMENT 

whole  cross-section  of  the  shaft  is  filled  with  broken  fire-brick. 
Above  this  compartment  the  third  compartment  is  formed  by  a 
grating  of  bricks,  made  of  a  mixture  of  80  per  cent,  magnesite 
and  20  per  cent.  Portland  cement.  On  this  grating  the  balls  of  ce- 
ment mixture  are  heaped  up  to  the  top  of  the  compartment,  which 
is  about  8  inches  high.  The  cover  consists  of  a  perforated  clay 
tile  upon  which  are  piled  broken  bricks.  The  clinker  compart- 
ment is  accessible  from  the  outside  by  means  of  a  door  which  is 
closed  by  a  fire-brick  plug  which  can  be  removed  and  the  clinkers 
withdrawn  and  examined. 

To  start  the  furnace,  a  small  amount  of  paper  and  wood  is  placed 
upon  the  pan  through  a  hole  provided  for  this  purpose.  The  oil 
on  coming  in  contact  with  the  hot  pan  is  vaporized  and  mixes 
with  the  air  in  the  compartment  filled  with  broken  brick.  The 
time  required  for  a  burn  in  this  kiln  is  about  two  hours.  By 
removing  the  pan  bricks  and  broken  pieces  of  brick  this  kiln  can 
also  be  used  for  burning  with  coke. 

When  large  quantities  of  cement  are  to  be  burned  a  small  shaft 
kiln  made  of  fire-brick  and  provided  with  grate  bars  can  be  used. 
The  cement  mixture  and  coke  being  charged  in  alternate  layers 
after  the  furnace  is  well  heated  up  and  a  bed  of  hot  coals  is  ob- 
tained on  the  grate  bars.  The  temperature  of  such  a  kiln  can  be 
greatly  increased  by  providing  means  of  blowing  air  through  the 
grate  bars. 

Prof.  E.  D.  Campbell,  of  the  University  of  Michigan,  used  in 
his  experimental  work  a  small  rotary  kiln  consisting  of  an  iron 
pipe,  8  inches  in  diameter  and  32  inches  long.  This  was  lined 
with  four  sections  of  hard  burned  magnesite  pipe,  3  inches  in- 
ternal diameter,  and  was  revolved  by  means  of  a  ]/2 -horse-power 
motor,  at  a  speed  of  one  revolution  in  85  seconds.  It  was  fired 
by  means  of  a  Hoskins  gasoline  burner  under  an  air  pressure  of 
50  pounds. 

After  sorting  the  clinker  it  is  crushed  and  ground  in  the  jar 
mill  mentioned  before,  the  degree  of  fineness  being  regulated  by 
conditions.  Plaster  or  gypsum  must,  of  course,  be  added  to  slow 
the  set  of  the  resulting  cement  and  may  be  ground  in  with  the 
clinker. 


APPENDIX. 

TABLES. 


TABLE  XLVI.— THE  ATOMIC  WEIGHTS  OF  THE  MORE   IMPORT- 
ANT ELEMENTS.     0  =  16. 


Name 

Symbol 

Weight                        Name 

Symbol 

Weight 

Al 
Sb 
As 
Ba 
Bi 
B 
Br 
Cd 
Ca 
C 
Cl 
Ch 
Co 
Cu 
F 
Au 
H 
T 

27.1 
120.2 

75-o 
137-4 
208.5 

II.O 

79.96 
112.4 
40.1 

12.0 

35-15 
52-  i 
59-o 
63.6 
19.0 
197.2 
1.008 

T26  O7 

Fe 
Pb 
Mg 
Mn 
Hg 
Ni 
N 
O 
P 
Pt 
K 
Si 

AS 

Na 
Sr 

a 

Sn 
7.n 

55-9 
206.9 
24.36 

55-o 
200.  o 

53.7 
14.04 
16.0 
31.0 
194.8 

39-15 
28.4 

107.93 
23-05 
87.6 
32.06 
119.0 
6=;  A 

Lead    

\rsenic  

Magnesium  

Xickel  

Phosphorus  

Platinum    ...... 

Potassium  

Cobalt    

Silver  

Gold       

Sulphur  

Tin 

Zino  .  , 

TABLE  XLVII. -FACTORS. 


Found. 

Sought. 

Factor. 

Found. 

Sought. 

Factor. 

MS 

CaS 
CaCO8 
CaO 
CaC03 
CaSO4 
C 
CaCOs 
MgCO, 
HC1 
Fe203 
FeO       • 
FeO 

0.50000 
1.7847 
0.41185 

0.73504 
1.8872 
0.27272 
2.2743 
I.9I54 
0.25424 
1.4284 
1.2856 
0.70007 

Mg2P207... 
Mg2P207... 
Mg2P,,07..- 
K2PtCl6  ... 
K2PtCl6  .  .  . 
I  BaSO,  
BaSO4  
BaSO4  
BaS04  
BaSO4  
!  BaSO4  
BaSO4  
1 

MgO 
MgC03 
&08 

K2O 
KC1 
S 
SO, 
H2SO4 
CaS04 
(CaS04)2H20 
CaSO4.2H2O 
CaS 

0.36190 
0.75722 
o.  63809 

0.19398 
0.53076 

0.13734 
0.34291 
0.42006 

:    0.58565 
0.62184 
o.7375o 
0.30895 

CaO 

OaSO 

CaSO 

CaS 

co2  

CO 

V.V/|   •  • 

CO 

\_W2 

Ao-ri  . 

-pp 

•pp 

"Rp  O 

37^  PORTLAND  CEMENT 

TABLE  XLVIII.-FOR  CONVERTING  Mg2P2O7  TO  MgO. 


&oS  . 

tc  Wigjy 
"cS  fcca 
8^«| 
g^tf'l 

Grams  of  Mg2P2O7  weighed. 

.00 

.01 

.02 

•03 

.04 

•05 

.06 

.07 

-  .08 

.09 

.00  .  .. 

.0138 

.OI39 

.0141 

.0142 

.0144 

.0145 

.0146 

.0148 

.0149 

.0151 

.10  .  .  . 

.0152 

•0153 

.0155 

.0156 

.0158 

•0159 

.Ol6o 

.0162 

.0163 

.0164 

.20-  .- 

.Ol66 

.0167 

.0168 

.0170 

.OI7I 

.0173 

.0174 

•0175 

.0177 

.0178 

.30  ... 

.0180 

.Ol8l 

.0182 

.0184 

.0185 

0.186 

.0188 

.0189 

.0191 

.OI92 

.40  ... 

.0193 

•0195 

.OI96 

.0197 

.0199 

.O2OO 

.O2O2 

.O2O3 

.O2O4 

.0206 

.50... 

.0207 

.O2O9 

.O2IO 

.O2II 

.0213 

.0214 

.0215 

.O2I7 

.0218 

.0220 

.60... 

.0221 

.0222 

.0224 

.0225 

.0226 

.0228 

.0229 

.0231 

.0232 

•0233 

.70... 

•0235 

.0236 

.0238 

.0239 

.0240 

.O242 

.0243 

.0244 

.0246 

.0247 

.80... 

.0249 

.0250 

.0251 

•0253 

.0254 

•0255 

.0257 

.0258 

.0260 

.O26l 

.90... 

.O262 

.0264 

.0265 

.0267 

.0268 

.0269 

.0271 

.0272 

.0273 

.0275 

2.00  .  •  • 

.0276 

.0278 

.0279 

.O28O 

.0282 

.0283 

.0285 

.0286 

.0287 

.0289 

2.10  •  -. 

.0290 

.0291 

.0293 

.0294 

.0296 

.0297 

.0298 

.0300 

.0301 

.0302 

2.20  •  .. 

.0304 

•°3°5 

.0307 

.0308 

.0309 

.0311 

.0312 

.0314 

•03I5- 

.0316 

2.30... 

.0318 

.0319 

.O32O 

.0322 

•0323 

.0325 

.0326 

.0328 

.0329 

.0330 

2.40-  -• 

•0331 

•0333 

•0334 

.0336 

•0337 

.0338 

.0340 

.0341 

•0343 

•0344 

2.50... 

•0345 

.0347 

.0348 

•0349 

.0351 

.0352 

•0354 

•0355 

•0356 

.0358 

a.  60.  -  . 

•0359 

.0360 

.0362 

•0363 

•0365 

.0366 

.0367 

.0369 

.0370 

.0372 

2.70... 

•0373 

•0374 

.0376 

•0377 

.0378 

.0380 

.0381 

.0383 

.0384 

•0385 

2.80... 

.0387 

.0388 

.0389 

.0391 

.0392 

•0394 

•°395 

.0396 

.0398 

•0399 

2.90  .  .  . 

.O4OO 

.0402 

.0403 

.0405 

.0406 

.0407 

.0409 

.O4IO 

.O4I2   .0413 

3.00... 

.0414 

.0416 

.0417 

.0419 

.0420 

.O42I 

.0423 

.0424 

.0425   .0427 

3.10... 

.0428 

.0429 

.0431 

.0432 

.0434 

•0435 

.0436 

.0438 

.0439   .0441 

3.20... 

.0442 

•0443 

.0445 

.0446 

.0447 

.0449 

.0450 

.0452 

.0453   .0454 

3-3°  ••• 

.0456 

•0457 

.0458 

.0460 

.0461 

.0463 

.0464 

0.465 

.0467   .0468 

3.40... 

0.470 

.0471 

.0472 

.0474 

•0475 

.0477 

.0478 

.0479 

.0481    .0482 

3-50  •-• 

.0483 

.0485 

.0486 

.0488 

.0489 

.0490 

.0492 

•0493 

.0495 

.0497 

TABLE  XLIX.— FOR  CALCULATING  THE  PERCENTAGE  OF  LIME 
OR  CARBONATE  OF  LIME  WITH  ONE-HALF  GRAM  SAMPLE.1 


55-0  C. 

C. 

55-1  C 

.  C. 

55-2 

C.  C. 

CaO 

CaC03 

CaO 

CaC03 

CaO 

CaCOg 

I 

1.018 

1.816 

i 

1.016 

1.814 

i 

1.015 

i.  812 

2 

2.036 

3.632 

2 

2.032 

3-628 

2 

2.030 

3.624 

3 

3.054 

5.448 

3 

3.048 

5.442 

3 

3-045 

5-436 

4 

4.072 

7.264 

4 

4.064 

7.256 

4 

4.060 

7.248 

5 

5.090 

9.080 

5 

5.080 

9.070 

5 

5-075 

9.060 

6 

6.108 

10.896 

6 

6.096 

10.884 

6 

6.090 

10.872 

7 

7.126 

12.712 

7 

7.112 

12.698 

7 

7-105 

12.684 

8 

8.144 

14-528 

8 

8.128 

14.512 

8 

8.120 

14.496 

9 

9.162 

16.344 

9 

9.144 

16.326 

9 

9-135 

16.308 

1  Chemical  Engineer,  I.,  42. 


APPENDIX  TABLES 


379 


TABLE  XLIX.— (Continued}. 


55-3  C. 

C. 

55-4  C. 

C. 

55-5 

C.  C. 

CaO 

CaC03 

CaO 

CaCO3 

CaO 

CaC03 

I 

1.013 

1.808 

i 

I.  Oil 

1.805 

i 

1.009 

1.801 

2 

2.026 

3.616 

2 

2.022 

3.610 

2 

2.018 

3.602 

3 

3-°39 

5-424 

3 

3-033 

5.4I5 

3 

3.027 

5-403 

4 

4.052 

7.232 

4 

4.044 

7.220 

4 

4.036 

7.204 

5 

5-o65 

9.040 

5 

5-055 

9.025 

5 

5-045 

9.005 

6 

6.078 

10.848 

6 

6.066 

10.830 

6 

6.054 

10.806 

7 

7.091 

12.656 

7 

7.077 

12.635 

7 

7.063 

12.607 

8 

8.104 

14.454 

8 

8.088 

14.440 

8 

8.072 

14.408 

9 

9.117 

16.272 

9 

9.099 

16.245 

9 

9.081 

16.209 

55-6  C. 

C. 

55-7  C. 

C. 

55-8 

C.  C. 

CaO 

CaCO3 

CaO 

CaCO4 

CaO 

CaCO3 

i 

1.007 

1.797 

i 

1.005 

1.794 

i 

1.004 

1.792 

2 

2.014 

3-594 

2 

2.OIO 

3-588 

2 

2.008 

3.584 

3 

3.021 

5-391 

3 

3-OI5 

5-382 

3 

3.012 

5.376 

4 

4.028 

7.188 

4 

4.020 

7.176 

4 

4.010 

7.168 

5 

5-035 

8.985 

5 

5-025 

8.970 

5 

5.020 

8.960 

6 

6.042 

10.782 

6 

6.030 

10.764 

6 

6.024 

10.752 

7 

7.049 

12.579 

7 

7-035 

12.558 

7 

7.028 

12.544 

8 

8.056 

14.376 

8 

8.040 

14.352 

8 

8.032 

H.336 

9 

9.063 

16.173 

9 

9-°45 

16.146 

9 

9.036 

16.128 

55-  9  C. 

C. 

56.0  C. 

C. 

56.1 

C.  C. 

CaO 

CaC03 

CaO 

CaCO3 

CaO 

CaC03 

i 

i.  002 

1.789 

i 

I.OOO 

1.785 

i 

0.998 

1.782 

2 

2.004 

3-5/8 

2 

2.OOO 

3-570 

2 

1.996 

3-564 

3 

3.006 

5-367 

3 

3.000 

5-355 

3 

2-995 

5.346 

4 

4.008 

7.'56 

4 

4.OOO 

7.140 

4 

3-993 

7.128 

5 

5.010 

8-945 

5 

5.000 

8.925 

5 

4.991 

8.910 

6 

6.OI2 

10.734 

6 

6.000 

10.710 

6 

5.989 

10.692 

7 

7.014 

12.523 

7 

7.000 

12.495 

7 

6.987 

12.474 

8 

8.016 

14.312 

8 

8.000 

14.280 

8 

7.986 

14.256 

9 

9.018 

16.  101 

9 

9.000 

16.065 

9 

8.984 

16.038 

56.2  C. 

C. 

56.3  c. 

C. 

56.4 

C.  C. 

CaO 

'   CaC03 

CaO 

CaC03 

CaO 

CaC03 

i 

0.996 

1.779 

i 

0-995 

1.776 

i 

0-993 

1-773 

2 

1.992 

3.558 

2 

1.990 

3-552 

2 

1.986 

3.546 

3 

2.988 

5-337 

3 

2.985 

5-328 

3 

2-979 

5.319 

4 

3.984 

7.  1  16 

4 

3-980 

7.104 

4 

3-972 

7.092 

5 

4.980 

8.895 

5 

4-975 

8.880 

5 

4-965 

8.865 

6 

5-9/6 

10.674 

6 

5-970 

10.656 

6 

5-958 

10.638 

7 

6.972 

12.453 

7 

6.965 

12.432 

7 

6.951 

12.411 

8 

7.968 

14.232 

8 

7.960 

14.208 

8 

7-944 

14.184 

9 

8.964 

16.011 

9 

8-955 

15-984 

9 

8-937 

15-957 

38O  PORTLAND 

TABLE  XLIX.— (Continued}. 


56.5  c. 

C. 

56.6  C. 

C. 

56.7  C. 

C. 

CaO 

CaC03 

CaO 

CaCO, 

CaO 

CaCO, 

1 

0.991 

1.770 

i 

0.989 

1.767 

! 

0.988 

1.764 

2 

1.982 

3-540 

2 

1.978 

3-534 

2 

1.976 

3-528 

3 

2-973 

5-310 

3 

2.967 

5-301 

3 

2.964 

5.292 

4 

3-964 

7.080 

4 

3.956 

7.068 

4 

3-952 

7.056 

5 

4-955 

8.850 

5 

4-945 

8.835 

5 

4.940 

8.820 

6 

5-946 

10.620 

6 

5-934 

10.602 

6 

5.928 

10.584 

7 

6-937 

12.390 

7 

6.923 

12.369 

7 

6.916 

12.348 

8 

7.928 

14.160 

8 

7.912 

14.136 

8 

7.904 

14.112 

9 

8.919 

15.930 

9 

8.901 

15-903 

9 

8.892 

15-8/6 

56.8  C. 

C. 

56.9  C. 

C. 

57.0  C. 

C. 

CaO 

CaCQ, 

CaO 

CaCO, 

CaO 

CaCO3 

I 

0.986 

1.761 

i 

0.984 

1-757 

i 

0.983 

I-754 

2 

1.972 

3-522 

2 

1.968 

3.514 

2 

1.966 

3-508 

3 

2.958 

5-283 

3 

2.952 

5-271 

3 

2.949 

5.262 

4 

3-944 

7.044 

4 

3-936 

7.028 

4 

3-932 

7.016 

5 

4-930 

8.805 

5 

4.920 

8.785 

5 

4.915 

8.770 

6 

S-9'6 

10.566 

6 

5-904 

10.542 

6 

5-898 

10.524 

7 

6.902 

12.327 

7 

6.888 

12.299 

7 

6.881 

12.278 

8 

7.888 

14.088 

8 

7.872 

14.056 

8 

7.864 

14.032 

9 

8.874 

15-849 

9 

8.856 

15-813 

9 

8.847 

15786 

The  first  column  of  each  table  gives  the  number  of  cubic 
centimeters  of  permanganate  required  by  0.5  gram  of  calcite  (see 
page  1 86),  and  the  second  and  third  columns  show  the  corres- 
ponding percentages  of  calcium  oxide  and  calcium  carbonate 
respectively  where  a  half  gram  sample  has  been  taken. 

Example  of  the  use  of  tables. — Suppose  0.5  gram  of  calcite 
takes  55.6  C.  C.  of  permanganate,  then  write  the  values  found  in 
the  table  headed  55.6  C.  C.  on  a  card  and  stand  near  the  burette 
table.  The  writer  usually  notes  the  CaO  values  in  red  nk  and 
the  CaCO3  in  black  to  avoid  confusing  them. 

Now  suppose  we  analyze  a  limestone  and  find  it  requires 
51.3  C.  C.  then  the  percentage  of  lime  and  carbonate  of  lime  may 
be  calculated  from  the  table  as  follows  : 


CaO 

CaCO., 

50.0 

C.  C. 

50.35 

89.85 

1.0 

C.  C. 

1.007 

1-797 

.3 

C.  C. 

.3021 

•5391 

51.3  5I-6591  92.1661 


INDEX. 


Adulteration,   Detection  of — in    Portland   Cement 366 

Aiken's   Method  of  Making  Briquettes    345 

Air    Separators 150 

Alit     20 

Alkalies,   Determination  of  —in   Cement    220 

Alkalies.  Influences  of — on  the  properties  of  Portland  Cement 30 

Alkali   Waste    47 

Alumina.  Influence  of — on  the  Properties  of  Portland  Cement  27 

Analyses  of  Cement  Rock,  Table  of 39 

Analytical    Methods    166 

Analyses  of  Clay,  Table  of   45 

Analyses  of  Limestone,  Table  of  36 

Analyses  of  Marl,  Table  of  43 

Analyses  of  Portland  Cement,  Table  of  16,  17 

Analyses  of  Shale,  Table  of 46 

Analysis  of  Cement  Mixtures,  Methods  for  ' 225 

Analysis  of  Cement  Rock,  Methods  for   254 

Analysis  of  Clay,  Methods  for   261 

Analysis  of  Gypsum,  Methods  for  269 

Analysis  of  Limestone,  Methods  for   254 

Analysis  of  Marl,  Methods  for 254 

Analysis  of  Plaster  of  Paris,  Methods  for  269 

Analysis  of  Portland  Cement,  Methods  for   167 

Analysis  of  Shale,  Methods  for   261 

Analysis  of  Slurry,  Methods  for   225 

Aspdin,    Joseph 2 

Atomic  Weights,   Table  of    377 

Balance   for  Testing   Fineness    292 

Ball    Mill 92 

Bauschinger's    Calipers     356 

Belit     21 

Blake  Crusher    86 

Blast   Furnace   Slag    46 

Bohme   Hammer    . 342 

Boiling  Test  for  Soundness  355 

Bramwell's  Improved  Vicat  Needle   302 

Briquettes,   Forms   of    ' 317,  322 

Briquettes,    Marking    328 

Briquettes,  Storage  of   327 

Burning,  Chemical  Changes  During 123 

Burning,   Degree  of 132 

Burning,  Excess  of  Air  Used  in 139 

Burning,    Regularity   of    129 

Burning,  Temperature  of  131 

Burning,  The  Raw  Materials   100 

Burning,  Thermo-Chemistry  of   133 

Burning,   Trial    Kiln   for    372 

Calcimeter,    Scheibler's    243 


3&2  INDEX 

Calcium  Carbonate,  Rapid  Methods  for  Determining— in  Cement 

Mixtures    231 

Calcium  Chloride  Test  for  Soundness 355 

Calcium  Sulphide,  Determination  of — in  Cement  204 

Capacity  of  Various  Grinding  Mills   97 

Carbon   Dioxide,   Determination   of — in   Cement    .  208 

Celit    21 

Cement  Mixture,  Complete  Analysis  of   '. .  248 

Cement  Mixture,  Proportioning 52 

Cement    Rock     35 

Cement  Rock,  Analysis  of   254 

Clay ' 44 

Clay,  Analysis   of    261 

Clips   for  Briquettes    321,  338 

Coal-Burning    Apparatus    1 12 

Coal   Dryers    115 

Coal    Grinding    114 

Coal,  kind  for  Cement  Burning  114 

Composition  of  Portland  Cement   15 

Conveyors     99 

Cooling    Clinker    146 

Cost  of  Portland  Cement  Manufacture   163 

Cost  of  Portland  Cement  Plant  f 61 

Crushers     84 

Dietsch  Kiln   103 

Dome   Kiln    100 

Dredge  for  Excavating  Marl    73 

Dryer   for  Coal    115 

Dryer  for  Stone,  Clay,  Etc 77 

Emerick  Air  Separator   152 

Equipment  of  Portland  Cement  Plants    157 

Excavating  Marl 73 

Expansion  of  Cement,  Measurement  of  356,  357 

Factors  for  Calculating  Analyses   377 

Faija's    Mixer 341 

Faija's  Test  for  Soundness   351 

Fairbank's  Automatic  Cement  Testing  Machine   329 

Felit    21 

Ferric  Oxide,  Determination  of  191 

Ferric  Oxide,  Influence  of — on  the  Properties  of  Portland  Cement.  ...     28 

Fineness  of  Cement,  Method  of  Taking 291 

Fineness  to  which  Raw  Material  Should  be  Ground 98 

Flour,   Determination   of — in   Cement    298 

Gates   Crusher    85 

Gilmore's   Needles   301 

Gooch   Crucible 184 

Grappiers,  Analysis  of  Tiel 18 

Griffin  Mill,  Single  Roll   87 

Griffin  Mill,  Three  Roll   89 

Grinding,  Effect  of — on  Soundness    360,  361 

Grinding    Machinery    84 

Gypsum     48 

Gypsum,    Analysis    of 269 

Hardening  of  Cement,  Theory  of   18,  24 

History  of  the  American  Portland  Cement  Industry  I 

Hoffmann   Ring   Kiln    102 


INDEX  383 

Huntington   Mill    .» 91 

Hydraulic    Index     19 

Hydrochloric  Acid,  Specific  Gravity  of  234 

Inspection   of  Cement    272 

Iron,    Determination    of    191 

Jackson's  Apparatus  for  the  Rapid  Determination  of  Sulphates 201 

Jackson's  Apparatus  for  Specific  Gravity 281 

Jameson's  Briquette  Making  Machine   343 

Jar-Mill   for  Laboratory   Grinding    373 

Johnston    Kiln     101 

Johnson's  Cement  Testing  Machine   334 

Kent    Mill 149 

Kiln,    Experimental    374 

Kilns,  Forms  of 100 

Kiln  Test  for  Soundness   354 

Kominuter    95 

LeChatelier's   Apparatus   for    Specific   Gravity    278 

LeChatelier's    Calipers     357 

LeChatelier's  Theories  as  to  Composition  of  Portland  Cement 18 

Lime,  Influence  of — on  the  Properties  of  Portland  Cement   25 

Lime,  Rapid  Determination  of — in  Portland  Cement  189 

Limestone     34 

Limestone,    Analysis    of    254 

Lining  for  Rotary   Kilns 121 

Loss  on  Ignition,  Determination  of — in  Portland  Cement 208 

Maclay's  Test  for  Soundness   352 

Magnesia,  Influence  of  on  the  Properties  of  Portland  Cement 29 

Manganese,  Determination  of — in  Portland  Cement    223 

Manufacture  of  Portland  Cement   33 

Marl    40 

Marl,  Analysis  of   254 

Mixing  Mortar  for  Tensile  Strength  Tests  318,  325 

Mixing  Raw  Materials  for  Portland  Cement  Manufacture  75 

Molding   Briquettes    , 319 

Molds   for  Briquettes    317,  323 

Mortar    Mixers    341 

Natural   Cement    3,  4 

Natural  Gas  for  Cement  Burning 121 

Newberry's  Method  for  Magnesia  . . .  ." 259 

Newberry's  Theory  as  to  the  Composition  of  Portland  Cement 19 

Normal   Consistency    299,  303 

Olsen's  Automatic  Cement  Testing  Machine  ". 332 

Packing   Cement    154 

Parker's   Roman   Cement    2 

Pfeiffer  Air   Separator 150 

Phosphoric  Acid,  Determination  of — in  Portland  Cement   222 

Plaster  of   Paris    48 

Plaster  of  Paris,  Analysis  of   269 

Porter's   Testing  Machine    336 

Powdered  Coal,  Method  of  Burning   112 

Power  Plant  of  a  Portland  Cement  Mill 155 

Producer  Gas  for  Burning   . . . . 1 18 

Production  of  Natural  Cement  in  the  United  States   6,  7 

Production  of  Portland  Cement  in  the  LTnited  States n,  12,  13,  14 

Proportioning  the  Raw  Materials  in  Portland  Cement  Manufacture...     52 
Pug   Mill    73 


384  INDEX 

Puzzolan    Cement    3 

Quarrying  Rock,   Etc 71 

Raw   Materials,  Analysis  of    252 

Raw  Materials  for  the  Manufacture  of  Portland  Cement  33 

Raw  Materials,   Proportioning    52 

Richardson's  Work  on  the  Composition  of  Portland  Cement   21 

Riehle   Cement   Testing   Machine    331 

Rise  in  Temperature  During   Setting    305 

Roman    Cement    2,  3 

Rosendale    Cement 3,  4 

Rotary   Kiln 106 

Sampler    for    Cement    168,  169 

Sampler  for  Raw  Materials    227 

Sampling   Cement    167 

Sampling   Cement   Mixture    225 

Sampling   Cement   Rock   252 

Sampling    Clay     253 

Sampling    Limestone 252 

Sampling    Marl    254 

Sampling    Shale     253 

Sampling    Slurry    229 

Sand,    Standard    , 316,  321 

Saylor,  David  O.,  8 

Schoefer    Kiln    105 

Schumann-Candlot  Apparatus   for   Specific   Gravity    280 

Scraper   for   Cleaning   Molds    324 

Seasoning,    Effect    of — on    Soundness    359 

Setting  Time,   Factors   Influencing    303 

Setting  Time,  Influence  of  Calcium  Chloride  Upon    310 

Setting  Time,  Influence  of  Slaked  Lime  Upon    314 

Setting  Time,  Influence  of  Storage  Upon   311 

Setting  Time,  Influence  of  Sulphates  Upon   306 

Setting  Time,  Influence  of  Temperature  Upon  304 

Setting  Time,  Influence  of  Water  Used  to  Gauge  Mortar  Upon   305 

Setting  Time,  Test  for    299,  301 

Shale     45 

Shale,   Analysis   of    261 

Shimer's  Crucible  for  Determining^  Water  and  Carbon  Dioxide  208 

Snimer's  Filter     Tube  for  Barium" Sulphate  206 

Shimer's  Reduction  for   Iron 195 

Sieves   for   Testing    Fineness    291 

Sieves  for  Testing  Fineness,  Errors  in  293 

Sieve   Tests,   Limitations   of    294 

Silica,  Influence  of — on  the  Properties  of  Portland  Cement  27 

Silicates,  Determination  of — in  the  Raw  Materials   247 

Slag    Cement    3 

Slurry,   Complete  Analysis  of    225,  248 

Slurry    Pumps    75 

Smeaton,  John I 

Solid   Solution   Theory    23 

Soundness,  Effect  of  Fine  Grinding  Upon   360,  361 

Soundness,  Effect  of   Seasoning  Upon 359 

Soundness,  Effect  of  Sulphates  Upon 361 

Soundness,  Importance  of  Tests  for   35° 

Soundness,  Tests  for    35*,  352,  354,  355,  356,  357 

Soundness,  Value  of  Accelerated  Tests  for  362 


INDEX  385 

Specifications,    Uniform    277 

Specifications,  Uniform  —  for   Fineness 291 

Specifications,   Uniform —  for  Setting  Time 299 

Specifications,  Uniform  —  for  Soundness  351 

Specifications,  Uniform  —  for  Specific  Gravity   278 

Specifications,  Uniform  —  for  Tensile  Strength 316 

Specific  Gravity  of  Cement,  Determination  of 278 

Specific  Gravity  of  Cement,  Value  of  Test  289 

Standard  Acid,   Preparation  of    233 

Standard   Alkali,    Preparation   of    232 

Standard  Samples,   Preparation  of   235 

Steinbriich    Mixer    340 

Stock    Houses    153 

Stone    Houses    75 

Sulphates,  Determination  of — in  Portland  Cement   200 

Sulphur,  Determination  of — in  Portland  Cement  203 

Sulphur,  Influence  of — on  the  Properties  of  Portland  Cement 30 

Table    for    Mixing   Mortar    325 

Table   for   Titrations    187 

Testing    Machines     329 

Tensile    Strength     316 

Tensile  Strength,  Drop  In    346,  347 

Tensile  Strength,  Effect  of  Grinding  Upon   347,  348 

Tensile  Strength,  Influence  of  Percentage  of  Water  Upon  326 

Tensile  Strength,  Method  of  Testing   316 

Tensile   Strength  of  Unsound   Cement    346 

Titanium,  Determination  of — in  Portland  Cement   224 

Three  Roll  Griffin  Mill    89 

Tornebohm's  Investigations  on  the  Composition  of  Portland  Cement..  20 

Trial  Burnings  of  Raw  Materials  372 

Tube   Mill 95 

Uniformity,  Lack  of  in  Tensile  Tests 339 

Unsound   Cement,   Causes   of 358 

Valuation  of  Raw  Materials   49 

Vicat   Needle    300 

Waste  Heat  of  Kilns,  Utilization  of  141 

Water,  Combined,  Determination  of  in  Portland  Cement  208 

Water,  Hygroscopic,  Determination  of  in  Portland  Cement   218 

Water,  Percentage  of  for  Sand  Briquettes   320 

Water,  Presence  of  in  Portland  Cement 31 

Wet  Process  of  Mixing  the  Raw  Materials   78 


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